Search

We begin with an $E_{8}\times E_{8}$ Heterotic model broken to an $SU(5)_{gauge} \times U(1)_{X}$ and a twin $SU(5)_{gauge} \times U(1)_{X}$, where one $SU(5)$ and its spectrum is identified as the visible sector while the other can be identified as a hidden twin sector. In both cases we obtain the minimal supersymmetric standard model (MSSM) spectrum after Wilson-line symmetry-breaking enhanced by a low energy R-parity and $\mathbb{Z}_4^R$ symmetry. We argue that there will not be any observable proton decay in this model, Comment: 5 pages, fixed a reference and added some clarification

In this talk, given at Corfu 2022 Workshop on the Standard Model and Beyond, I present work in collaboration with Junichiro Kawamura,Ref.~[arXiv:2212.00840]. The talk is also based on a number of papers on a Global $SU(5)$ F-theory GUT in collaboration with Herb Clemens. In the model $SU(5)$ is broken to the MSSM via a Wilson line. This is accomplished (without problems with vector-like exotics) by simultaneously describing the F-theory model and its Heterotic dual. The model has a twin MSSM sector and it's the neutrino sector of the field I consider in the talk., Comment: 16 pages, 5 figures, Talk given at Corfu 2022, Workshop on the Standard Model and Beyond

An additional generation of quarks and leptons and their SUSY counterparts, which are vector-like under the Standard Model gauge group but are chiral with respect to the new U(1)$_{3-4}$ gauge symmetry, are added to the Minimal Supersymmetric Standard Model (MSSM). We show that this model is a GUT and unifies the three SM gauge couplings and also the additional U(1)$_{3-4}$ coupling at a GUT scale of $\approx 5 \times 10^{16}$ GeV and explains the experimentally observed deviation of the muon $g-2$. We also fit the quark flavor changing processes consistent with the latest experimental data and look at the effect of the new particles on the $W$ boson mass without obviously conflicting with the observed masses of particles, CKM matrix elements, neutrino mixing angles, their mass differences, and the lepton-flavor violating bounds. This model predicts sparticle masses less than 25 TeV, with a gluino mass $\approx 2.3 - 3$ TeV consistent with constraints, and one of the neutralinos as the LSP with a mass of $\approx 480 - 580$ GeV, which is a potential dark matter candidate. The model is string theory motivated and predicts the VL quarks, leptons, a massive $Z'$ and two Dirac neutrinos at the TeV scale and the branching ratios of $\mu \longrightarrow e \gamma$, $\tau \longrightarrow \mu \gamma$ and $\tau \longrightarrow 3\mu$ with BR($\mu \longrightarrow e \gamma$) within reach of future experiments., Comment: 24+17 pages, 6 figures, 5 tables; minor changes and additions, references added

We analyze the neutrino phenomenology in an $SU(5)$ F-theory model with both a visible sector and a twin hidden sector. At low energies, the strong and weak scales of the two sectors may differ but the spectrum of states is described by the MSSM (MSSM$^\prime$) in the visible (twin) sectors. What is special about the model is that there are right-handed neutrinos which couple to both sectors via Yukawa couplings. As a result, assuming 3 right-handed neutrinos with a large mass much greater than the weak scale, at tree-level the seesaw mechanism results in 3 massive Majorana neutrinos and 3 massless ones. The massless neutrinos acquire mass via radiative corrections. In our analysis, the massless neutrinos are predominantly active neutrinos, while the massive neutrinos are predominantly sterile neutrinos. We fit the active neutrino masses and mixing angles and discuss the phenomenology of the lightest sterile neutrino. Finally we consider some possible scenarios for cosmology., Comment: 19 pages, 2 figures

Supersymmetry is a highly motivated theoretical framework, whose scale of breaking may be at PeV energies, to explain null searches at the Large Hadron Collider. SUSY breaking through a first order phase transition may have occurred in the early universe, leading to potential gravitational wave signals. Constructing a realistic model for gauge-mediated supersymmetry breaking, we show that such a transition can also induce masses for heavy right-handed neutrinos and sneutrinos, whose CP-violating decays give leptogenesis at the PeV scale, and a novel mechanism of neutrino mass generation at one loop. For the same models we predict the possible gravity wave signals, and we study the possibility of production of primordial black holes during the phase transition., Comment: 19 pages, 8 figures

In this report we discuss the main theories to understand the origin of baryon and lepton number violation in physics beyond the Standard Model. We present the theoretical predictions for rare processes such as neutrinoless double beta decay, proton decay, and neutron-antineutron oscillation, and overview the prospects to discover these rare processes in the near future. The possibility to observe baryon and lepton violating signatures at current and future colliders and through precision studies of other rare processes, and the testability of different baryogenesis mechanisms is discussed in detail. A healthy and broad experimental program looking for proton decay, neutrinoless double beta decay and neutron-antineutron oscillations is essential to make new discoveries in this field. These searches are carried out at various experimental facilities in the US and abroad, and use instrumentation arching across traditional HEP/NP boundaries. In addition, experiments such as those at the Large Hadron Collider could discover exotic baryon and/or lepton number violating signatures connected to low energy scale theories for neutrino masses, supersymmetric models with R-parity violation, new gauge theories or other mechanisms for physics beyond the Standard Model. The landscape presented in this report could be crucial to discover the underlying mechanism for neutrino masses and the matter-antimatter asymmetry in the universe., Comment: SNOWMASS 2021 REPORT, RF4: BARYON AND LEPTON NUMBER VIOLATING PROCESSES, RARE PROCESSES AND PRECISION MEASUREMENTS FRONTIER

We study the effects of vector-like leptons on the $W$ boson mass in a model with a vector-like $U(1)^\prime$ gauge symmetry. This model provides simultaneous explanations for the recent anomalies in the muon anomalous magnetic moment and the semi-leptonic decays of $B$ mesons. We found that the recent result of the $W$ boson mass precise measurement at CDF can be explained if the charged (neutral) vector-like lepton is lighter than 250 (80) GeV. The light vector-like leptons may not be excluded by collider experiments if these decay to a physical mode of the $U(1)^\prime$ breaking scalar field., Comment: 16 pages, 4 figures; ver2 matched to published version

We study the lepto-axiogenesis scenario in the minimal supersymmetric KSVZ axion model. Only one Peccei-Quinn (PQ) field and vector-like fields are introduced besides the MSSM with the type-I see-saw mechanism. The PQ field is stabilized by the radiative correction induced by the Yukawa couplings with the vector-like fields introduced in the KSVZ model. We develop a way to follow the dynamics of the PQ field, in particular we found a semi-analytical solution which describes the rotational motion under the logarithmic potential with including the thermalization effect via the gluon scattering which preserves the PQ symmetry. Based on the solution, we studied the baryon asymmetry, the effective number of neutrino, and the dark matter density composed of the axion and the neutralino. We found that the baryon asymmetry is successfully explained when the mass of PQ field is $\mathcal{O}({10^6~\mathrm{GeV}})$ ($\mathcal{O}({10^5~\mathrm{GeV}})$) with the power of the PQ breaking term being $10$ ($8$)., Comment: 28 pages, 8 figures and 1 table.: v2 minor corrections and references added: v3 matched to published version, 2 appendices added

We propose a novel possibility to detect a very distinctive signal with more than four muons originating from pair-produced vector-like leptons decaying to a muon-philic $Z^\prime$ boson. These new particles are good candidates to explain the anomalies in the muon anomalous magnetic moment and the $b\to s\ell\ell$ processes. The doublet (singlet) vector-like leptons lighter than 1.3 (1.0) TeV are excluded by the latest data at the LHC if $\mathrm{BR}(E\to Z^\prime \mu) = 1$. We also show that the excess in the signal region with more than five leptons can be explained by this scenario if the vector-like lepton is a weak singlet, with mass about 400 GeV and $\mathrm{BR}(E\to Z^\prime \mu) = 0.25$. The future prospects at the HL-LHC are discussed., Comment: 11+6 pages, 8 figures

In this paper we construct supersymmetric Pati-Salam (PS) models containing the minimal supersymmetric standard model and an invisible axion. The models include two discrete symmetries, $\mathbb{Z}_4^R \times \mathbb{Z}_N$, which maintain the $quality$ of the accidental Peccei-Quinn (PQ) symmetry and thus the solution to the strong CP problem. We require that the discrete anomaly conditions are satisfied for both $\mathbb{Z}_4^R \times G_{\rm PS}^2$ and $ \mathbb{Z}_N \times G_{\rm PS}^2$. The vacuum expectation value of the PQ field spontaneously breaks all the discrete symmetries. R-parity is violated if any of the PQ field(s) has an odd charge under $\mathbb{Z}_4^R$. We present two explicit models which we refer to as a minimal model where R-parity violation is extremely suppressed, and a non-minimal model where R-parity violation is significant. In the latter model, the neutralino becomes unstable even if it is the Lightest Supersymmetric Particle (LSP), and, in addition, there are new low-energy vector-like states. In both examples, R-parity violation is sufficiently suppressed such that the proton is stable., Comment: 32 pages, 9 tables

In this letter we analyze the relative scales for the GUT and twin sectors in the F-theory model discussed in Ref. \cite{Clemens-3}. There are a number of volume moduli in the model. The volume of the GUT surface in the visible sector {[}sector(1){]} (with the Wilson line GUT breaking) defines the GUT scale $M_{GUT}\sim2\times10^{16}~GeV$ as the unification scale with precise gauge coupling unification of $SU(3)\times SU(2)\times U(1)_{Y}$. We choose $\alpha_{GUT}^{-1}\sim24$. We are then free to choose the ratio $\alpha_{G}(2)/\alpha_{G}(1)=m_{1}/m_{2}$ with $m(1)$ and $m(2)$ independent volume moduli associated with the directions perpendicular to the two GUT surfaces. We then analyze the effective field theory of the twin sector(2), which may lead to a SUSY breaking gaugino condensate. Of course, all these results are subject to the self-consistent stabilization of the moduli., Comment: 5 pages, this revised version corrects some equations in the first version. The bottom line remains unchanged

The authors have proposed a global model for Heterotic $F$-theory duality with Wilson line symmetry-breaking and a $4+1$ split of the $F$-theory spectral divisor. Goals of this note are to treat the existence of right-handed neutrinos in our $F$-theory model, show that the $\mathbb{Z}_{2}$-action in our model breaks the $U\left(1\right)_{X}$-symmetry associated to the $4+1$ split to $\mathbb{Z}_{2}$-matter parity, and to identify Yukawa couplings for the MSSM matter fields., Comment: 15 pages

In this paper we present an in-depth analysis of a recently proposed Standard Model extension with a complete fourth generation of quarks and leptons, which are vector-like with respect to the Standard Model gauge group and charged under a new spontaneously broken vector-like $\mathrm{U(1)^\prime}$ gauge symmetry. The model is designed to explain the known muon anomalies, i.e. the observed deviations from Standard Model predictions in the anomalous magnetic moment of the muon, $\Delta a_\mu$, and in $b \rightarrow s \ell^+ \ell^-$ processes. We perform a global $\chi^2$ analysis of the data with $65$ model parameters and including $98$ observables. We find many points with $\chi^2$ per degree of freedom $\leq 1$. The vector-like leptons and the new heavy $Z^\prime$ are typically much lighter than a TeV and would, thus, be eminently visible at the HL-LHC., Comment: 80 pages, 9 figures and 21 tables

We begin with an $E_{8}\times E_{8}$ Heterotic model broken to an $SU(5)_{gauge}$ and a mirror $SU(5)_{gauge}$, where one $SU(5)$ and its spectrum is identified as the visible sector while the other can be identified as a hidden mirror world. In both cases we obtain the minimal supersymmetric standard model spectrum after Wilson-line symmetry-breaking enhanced by a low energy R-parity enforced by a local (or global) $U(1)_{X}$-symmetry. Using Heterotic/$F$-theory duality, we show how to eliminate the vector-like exotics which were obtained in previous constructions. In these constructions, the Calabi-Yau {[}CY{]} four-fold was defined by an elliptic fibration with section over a base $B_{3}$ and a GUT surface given by $K3/\mathbb{Z}_{2}=$ Enriques surface. In the present paper we construct a quotient CY four-fold fibered by tori with two elliptic structures given by a a pair of sections fibered over the Enriques surface. Using Heterotic/$F$-theory duality we are able to define the cohomologies used to derive the massless spectrum. Our model for the 'correct' $F$-theory dual of a Heterotic model with Wilson-line symmetry-breaking builds on prior literature but employs the stack-theoretic version of the dictionary between the Heterotic semi-stable $E_{8}$-bundles with Yang-Mills connection and the $dP_{9}$-fibrations used to construct the $F$-theory dual., Comment: 51 pages, corrected some typos

In a previous paper, the authors showed the advantages of building a $\mathbb{Z}_{2}$-action into an $F$-theory model $W_{4}/B_{3}$, namely the action of complex conjugation on the complex algebraic group with compact real form $E_{8}$. The goal of this paper is to construct the Fano threefold $B_{3}$ directly from the roots of $SU\left(5\right)$ in such a way that the action of complex conjugation is exactly the desired $\mathbb{Z}_{2}$-action and the quotient of this action on $W_{4}/B_{3}$ and its Heterotic dual have the phenomenologically correct invariants., Comment: 26 pages, 4 figures, Lemma 6 has been added in order to clarify the discussion, section 6 has been revised. Section 8 has been revised in order to correct a mistake in the original version

We consider the Standard Model (SM) with the addition of a $\mathrm{U(1)^\prime}$ gauge symmetry and a complete fourth family of quarks and leptons which are vector-like with respect to the full $\mathrm{SU(3)_C}\times \mathrm{SU(2)_L} \times \mathrm{U(1)_Y}\times \mathrm{U(1)^\prime}$ gauge symmetry. The model provides a unified explanation of experimental anomalies in $(g - 2)_\mu$ as well as $b \rightarrow s \ell^+ \ell^-$ decays. We find good fits to the deviations from the SM, while at the same time fitting all other SM observables. The model includes a new $Z^\prime$ gauge boson, a $\mathrm{U(1)^\prime}$-breaking scalar, and vector-like leptons all with mass of order a few $100$ GeV. It is consistent with all currently released high energy experimental data, however, it appears imminently testable with well designed future searches. Also precision flavor experiments, especially more accurate direct determinations of CKM matrix elements, would allow to probe the best fit points., Comment: 40 pages, 2 figures and 14 tables; Figure 2 replaced, references added

Finding the $F$-theory dual of a Heterotic model with Wilson-line symmetry breaking presents the challenge of achieving the dual $\mathbb{Z}_{2}$-action on the $F$-theory model in such a way that the $\mathbb{Z}_{2}$-quotient is Calabi-Yau with an Enriques $\mathrm{GUT}$ surface over which $SU\left(5\right)_{gauge}$ symmetry is maintained. We propose a new way to approach this problem by taking advantage of a little-noticed choice in the application of Narasimhan-Seshadri equivalence between real $E_{8}$-bundles with Yang-Mills connection and their associated complex holomorphic $E_{8}^{\mathbb{C}}$-bundles, namely the one given by the real outer automorphism of $E_{8}^{\mathbb{C}}$ by complex conjugation. The triviality of the restriction on the compact real form $E_{8}$ allows one to introduce it into the $\mathbb{Z}_{2}$-action, thereby restoring $E_{8}$- and hence $SU\left(5\right)_{gauge}$- symmetry on which the Wilson line can be wrapped., Comment: 23 pages, includes minor corrections

The Standard Model (SM) is amended by one generation of quarks and leptons which are vector-like (VL) under the SM gauge group but chiral with respect to a new $\mathrm{U}(1)_{3-4}$ gauge symmetry. We show that this model can simultaneously explain the deviation of the muon $g-2$ as well as the observed anomalies in $b\rightarrow s\mu^+\mu^-$ transitions without conflicting with the data on Higgs decays, lepton flavor violation, or $B_s-\bar{B}_s$ mixing. The model is string theory motivated and GUT compatible, i.e. UV complete, and fits the data predicting VL quarks, leptons and a massive $Z'$ at the $\mathrm{TeV}$ scale, as well as $\tau\to3\mu$ and $\tau\to\mu\gamma$ within reach of future experiments. The Higgs couplings to SM generations are automatically aligned in flavor space., Comment: 15 pages + Appendix, 4 figures, 4 tables; v2: added references

In this paper, we consider the Standard Model (SM) with one family of vector-like (VL) leptons, which couple to all three families of the SM leptons. We study the constraints on this model coming from the heavy charged lepton mass bound, electroweak precision data, the muon anomalous magnetic moment, lepton flavor violation, Higgs decay constraints and a recently measured lepton non-universality observable, $R_{K^{*0}}$. We find that the strongest constraints are coming from the muon $g-2, \ R_{\mu\mu}=\Gamma(h\to\mu\mu)/\Gamma(h\to\mu\mu)_\text{SM}, \ R_{\gamma\gamma}$ and $\text{BR}(\mu\to e\gamma)$. Although VL leptons couple to all three families of the SM leptons, the ratio of electron-VL to muon-VL coupling is constrained to be $\langle\lambda_e/\lambda_\mu\rangle\lesssim10^{-4}$. We also find that our model cannot fit the observed value of $R_{K^{*0}}$., Comment: 24 pages, 8 figures, 2 tables

Previous studies of a three family Yukawa unified supersymmetric grand unified theory (SUSY GUT) with SO(10) or Pati-Salam (PS) gauge symmetry proposed by Raby and students show that this model is able to fit low energy and inflation observables. However, the fit to low energy observables is not great especially for $\sin2\beta$, and up and down quark masses. In this paper, we show that by choosing PS as the gauge group and modifying the Yukawa sector, the low energy fit improves significantly while other qualities of the model are maintained. In particular, the lightest SUSY particle is the neutralino with mass of order 300 - 500 GeV, the lightest stop and sbottom have mass of order 3 - 5 TeV and the CP odd Higgs mass is of order 5 - 6 TeV, so we are in the decoupling limit for the light Higgs. In addition, we reinterpret gluino simplified model analyses by the ATLAS and CMS collaborations and find that the most stringent gluino mass bound for our model is $M_{\tilde{g}}\sim1.9\,\text{TeV}$. The current best fit point, consistent with this bound, with gluino mass $M_{\tilde{g}}=1.9\,\text{TeV}$ has $\chi^2/\text{dof}\approx1.12$, compared to the best fit point of the previous model with $\chi^2/\text{dof}=1.90$. We find that predictions for the electric dipole moment of the electron, the branching ratio $BR(\mu \rightarrow e \gamma)$ and the CP violating angle in the lepton sector, $\sin\delta$, are affected significantly as compared to previous results. In summary, we are unable to rule out this model or place an upper bound on gluino mass accessible by this run of the LHC because the $\chi^2/\text{dof}$ of this model is well below $2\sigma$ even for a gluino mass as high as 2.7 TeV. On the bright side, this means that this model is still viable and we might find low energy SUSY particles in the near future., Comment: 22 pages, 3 figures, 4 tables; Corrected typos

In this talk I discuss a supersymmetric Pati-Salam model of fermion masses and mixing angles which fits low energy data. The model is then extended to include an inflationary sector which is shown to be consistent with Bicep2-Keck-Planck data. The energy scale during inflation is associated with the PS symmetry breaking scale. Finally, the model is shown to be consistent with the observed baryon-to-entropy ratio necessary for Big Bang Nucleosynthesis. It turns out that only the heaviest right-handed neutrino decays produce the correct sign of the baryon-to-entropy ratio. Nevertheless, we obtain the observed value due to the process of instant preheating., Comment: 12 pages, 7 figures, talk presented at the CETUP* 2016 Conference, Lead, SD

In this paper, we extend the analysis of a Pati-Salam subcritical hybrid $F$-term inflation model, proposed by two of us, by studying the reheating and the baryogenesis (via leptogenesis) of the model. This SUSY GUT model is able to fit low energy electroweak precision data, LHC data, $b$-physics data, in addition to inflation observables such as the tensor-to-scalar ratio and the scalar spectral index. The reheating mechanism of this model is instant preheating due to the bosonic and fermionic broad parametric resonance, while the baryon-to-entropy ratio is obtained from the CP asymmetric right-handed (s)neutrinos decay. The phases in the neutrino Yukawa matrices are fixed by fitting to the low energy observables. With these phases, the heaviest right-handed (s)neutrinos decay to produce a lepton asymmetry with the correct sign, while the two lighter right-handed (s)neutrinos decay to produce the wrong sign. Consequently, the baryogenesis analysis is necessarily performed by including all three families of the right-handed (s)neutrinos., Comment: 44 pages, 7 figures, 2 tables

Axions may make a significant contribution to the dark matter of the universe. It has been suggested that these dark matter axions may condense into localized clumps, called "axion stars." In this paper we argue that collisions of dilute axion stars with neutron stars, of the type known as "magnetars," may be the origin of most of the observed fast radio bursts. This idea is a variation of an idea originally proposed by Iwazaki. However, instead of the surface effect of Iwazaki, we propose a perhaps stronger volume effect caused by the induced time dependent electric dipole moment of neutrons., Comment: 10 pages, published version without figure

In this paper we present a model of subcritical hybrid inflation with a Pati-Salam [PS] symmetry group. Both the inflaton and waterfall fields contribute to the necessary e-foldings of inflation, while only the waterfall field spontaneously breaks PS hence monopoles produced during inflation are diluted during the inflationary epoch. The model is able to produce a tensor-to-scalar ratio, $r < 0.09$ consistent with the latest BICEP2/Keck and Planck data, as well as scalar density perturbations and spectral index, $n_s$, consistent with Planck data. For particular values of the parameters, we find $r = 0.084$ and $n_s = 0.0963$. The energy density during inflation is directly related to the PS breaking scale, $v_{PS}$. The model also incorporates a $\mathbb{Z}_4^R$ symmetry which can resolve the $\mu$ problem and suppress dimension 5 operators for proton decay, leaving over an exact $R$-parity. Finally the model allows for a complete three family extension with a $D_4$ family symmetry which reproduces low energy precision electroweak and LHC data., Comment: 19 pages, 4 figures. v2: typo fixed, figure added, references added; v3: additional typos fixed

In this letter we have presented a novel version of "long-lived" gluinos in supersymmetric models with the gluino the lightest ordinary supersymmetric particle [LOSP] and axino LSP. Within certain ranges of the axion decay constant $f_a < 1 \times 10^{10}$ GeV, the gluino mass bounds are reduced to less than 1000 GeV. The best limits can be obtained by looking for decaying R-hadrons in the detector where the gluino decays to a gluon and axino in the calorimeters. SUSY models with a gluino LOSP can occur over a significant region of parameter space in either {\em mirage-mediation} or general gauge-mediated SUSY breaking models. The gluino LOSP is not constrained by cosmology, but in this scenario the axion/axino may be good dark matter candidates., Comment: 4 pages, 0 figures

We provide a systematic treatment of chemical equilibrium in the presence of a specific type of time dependent background. The type of time dependent background we consider appears, for example, in recently proposed axion/Majoron leptogenesis models [1,2]. In describing the chemical equilibrium we use quantities which are invariant under redefinition of fermion phases (we refer to this redefinition as a change of basis for short), and therefore it is a basis invariant treatment. The change of the anomaly terms due to the change of the path integral measure [3,4] under a basis change is taken into account. We find it is useful to go back and forth between different bases, and there are insights which can be more easily obtained in one basis rather than another. A toy model is provided to illustrate the ideas. For the axion leptogenesis model [1], our result suggests that at $T > 10^{13}$ GeV , when sphaleron processes decouple, and $\Gamma_{B+L} << H < \Gamma_L$ (where $H$ is the Hubble parameter at temperature $T$ and $\Gamma_L$ is the $\Delta L = 2$ lepton number violating interaction rate), the amount of $B-L$ created is controlled by the smallness of the sphaleron interaction rate, $\Gamma_{B+L}$. Therefore it is not as efficient as described. In addition, we notice an interesting modification of gauge boson dispersion relations at subleading order.

In this paper we analyze Yukawa unification in a three family SO(10) SUSY GUT. We perform a global $\chi^2$ analysis and show that SUSY effects do not decouple even though the universal scalar mass parameter at the GUT scale, $m_{16}$, is found to lie between 15 and 30 TeV with the best fit given for $m_{16} \approx 25$ TeV. Note, SUSY effects don't decouple since stops and bottoms have mass of order 5 TeV, due to RG running from $M_{GUT}$. The model has many testable predictions. Gauginos are the lightest sparticles and the light Higgs boson is very much Standard Model-like. The model is consistent with flavor and CP observables with the $BR(\mu \to e\gamma)$ close to the experimental upper bound. With such a large value of $m_{16}$ we clearly cannot be considered "natural" SUSY nor are we "Split" SUSY. We are thus in the region in between or "SUSY on the Edge.", Comment: 23 pages, 3 figures, 9 tables; Changed title, added references for Section 3.2; Typos corrected

Threshold corrections to the bottom quark mass are often estimated under the approximation that tan$\beta$ enhanced contributions are the most dominant. In this work we revisit this common approximation made to the estimation of the supersymmetric threshold corrections to the bottom quark mass. We calculate the full one-loop supersymmetric corrections to the bottom quark mass and survey a large part of the phenomenological MSSM parameter space to study the validity of considering only the tan$\beta$ enhanced corrections. Our analysis demonstrates that this approximation underestimates the size of the threshold corrections by $\sim$12.5% for most of the considered parameter space. We discuss the consequences for fitting the bottom quark mass and for the effective couplings to Higgses. We find that it is important to consider the additional contributions when fitting the bottom quark mass but the modifications to the effective Higgs couplings are typically $\mathcal{O}$(few)% for the majority of the parameter space considered., Comment: 24 pages, 9 figures, 1 table; error in analysis corrected, results substantially modified, version to be submitted to JHEP

In this paper we discuss search strategies at the LHC for light electroweak gauginos which are mostly Wino-like, Higgsino-like or an admixture. These states are typically degenerate with decay products that are less energetic and hence difficult to detect. In addition, their production cross-sections at a hadron collider are suppressed compared to colored states such as the gluinos. In order to detect these states one needs to trigger on initial or final state radiation. Many previous analyses have focussed on mono-jet and mono-photon triggers. In the paper we argue and show that these triggers are unlikely to succeed, due to the large background from QCD backgrounds for the mono-jet searches and the fact that the $p_T$ distribution of the mono-photons are rapidly decreasing functions of $p_T$. We show this with both an analytic calculation of photons in the initial state radiation and also a detailed numerical analysis. We then argue that mono-Z triggers, from Z decaying into charged leptons may well provide the best search strategy, in particular for Higgsino-like and mixed cases.

In this paper we present a novel formulation of chaotic hybrid inflation in supergravity. The model includes a waterfall field which spontaneously breaks a gauged $U_1(B-L)$ at a GUT scale. This allows for the possibility of future model building which includes the standard formulation of baryogenesis via leptogenesis with the waterfall field decaying into right-handed neutrinos. We have not considered the following issues in this short paper, i.e. supersymmetry breaking, dark matter or the gravitino or moduli problems. Our focus is on showing the compatibility of the present model with Planck, WMAP and Bicep2 data., Comment: 11 pages, 3 figures

In this paper we study Yukawa-unified SO(10) SUSY GUTs with two types of SO(10) boundary conditions: (i) universal gaugino masses and (ii) non-universal gaugino masses with effective "mirage" mediation. With these boundary conditions, we perform a global chi^2 analysis to obtain the parameters consistent with 11 low energy observables, including the top, bottom, and tau masses. Both boundary conditions have universal scalar masses and "just so" splitting for the up- and down-type Higgs masses. In these models, the third family scalars are lighter than the first two families and the gauginos are lighter than all the scalars. We therefore focus on the gluino phenomenology in these models. In particular, we estimate the lowest allowed gluino mass in our models coming from the most recent LHC data and compare these to limits obtained using simplified models. We find that the lower bound on M_gluino in Yukawa-unified SO(10) SUSY GUTs is generically ~1.2 TEV at the 1 sigma level unless there is considerable degeneracy between the gluino and the LSP, in which case the bounds are much weaker. Hence many of our benchmark points are not ruled out by the present LHC data and are still viable models which can be tested at LHC 14., Comment: 17 pages, 2 figures

In this talk we discuss SO(10) Yukawa unification and its ramifications for phenomenology. The initial constraints come from fitting the top, bottom and tau masses, requiring large $\tan\beta \sim 50$ and particular values for soft SUSY breaking parameters. We perform a global $\chi^2$ analysis, fitting the recently observed `Higgs' with mass of order 125 GeV in addition to fermion masses and mixing angles and several flavor violating observables. We discuss two distinct GUT scale boundary conditions for soft SUSY breaking masses. In both cases we have a universal cubic scalar parameter, $A_0$. In the first case we consider universal gaugino masses, and universal scalar masses, $m_{16}$, for squarks and sleptons; while in the latter case we have non-universal gaugino masses and either universal scalar masses, $m_{16}$, for squarks and sleptons or D-term splitting of scalar masses. We discuss the spectrum of SUSY particle masses and consequences for the LHC., Comment: 12 pages, talk presented at the VIIth International Conference on Interconnections between Particle Physics and Cosmology and CETUP* 2013, Lead, SD

We consider the results from the first run of LHC studied in the context of simplified models and re-interpret them for a particular SO(10) model with a non-simplified topology. Hadronic searches have been designed to obtain the best sensitivity for the simplified models. They require multiple b-jets in the final state. But we show that the bounds obtained from these searches are weaker in the case of the particular model studied here, since there are fewer b-jets., Comment: Snowmass 2013 white paper

In this paper we study an SO(10) SUSY GUT with Yukawa unification for the third generation. We perform a global chi^2 analysis given to obtain the GUT boundary conditions consistent with 11 low energy observables, including the top, bottom and tau masses. We assume a universal mass, m_{16}, for squarks and sleptons and a universal gaugino mass, M_{1/2}. We then analyze the phenomenological consequences for the LHC for 15 benchmark models with fixed m_{16} = 20 TeV and with varying values of the gluino mass. The goal of the present work is to (i) evaluate the lower bound on the gluino mass in our model coming from the most recent published data of CMS and (ii) to compare this bound with similar bounds obtained by CMS using simplified models. The bottom line is that the bounds coming from the same sign di-lepton analysis are comparable for our model and the simplified model studied assuming BR(gluino -> t tbar neutralino) = 100%. However the bounds coming from the purely hadronic analyses for our model are 10 - 20% lower than obtained for the simplified models. This is due to the fact that for our models the branching ratio for the decay gluino -> g neutralino is significant. Thus there are significantly fewer b-jets. We find a lower bound on the gluino mass in our models with M_{gluino} > 1000 GeV. Finally, there is a theoretical upper bound on the gluino mass which increases with the value of m_{16}. For m_{16} <= 30 TeV, the gluino mass satisfies M_{gluino} <= 2.8 TeV at 90% CL. Thus, unless we further increase the amount of fine-tuning, we expect gluinos to be discovered at LHC 14.

In this letter we analyze the consequences, for the LHC, of gauge and third family Yukawa coupling unification with a particular set of boundary conditions defined at the GUT scale, which we characterize as effective "mirage" mediation. We perform a global chi-squared analysis including the observables M_W, M_Z, G_F, alpha_em, alpha_s(M_Z), M_top, m_b(m_b), M_tau, BR(B -> X_s gamma), BR(B_s -> mu^+ mu^-) and M_{h}. The fit is performed in the MSSM in terms of 10 GUT scale parameters, while tanb and mu are fixed at the weak scale. We find good fits to the low energy data and a SUSY spectrum which is dramatically different than previously studied in the context of Yukawa unification., Comment: 12 pages. arXiv admin note: text overlap with arXiv:1212.0542

This paper is divided into two parts. In the first part we analyze the consequences, for the LHC, of gauge and third family Yukawa coupling unification with a particular set of boundary conditions defined at the GUT scale. We perform a global chi^2 analysis including the observables M_W, M_Z, G_F, 1/alpha_em, alpha_s(M_Z), M_t,m_b(m_b), M_tau, BR(B -> X_s gamma), BR(B_s -> mu^+ mu^-) and M_h. The fit is performed in the MSSM in terms of 9 GUT scale parameters, while tan beta and mu are fixed at the weak scale. Good fits suggest an upper bound on the gluino mass, M_gluino \lesssim 2 TeV. This constraint comes predominantly from fitting the bottom quark and Higgs masses (assuming a 125 GeV Higgs). Gluinos should be visible at the LHC in the 14 TeV run but they cannot be described by the typical simplified models. This is because the branching ratios for gluino -> t tbar neutralino, b bbar neutralino, t bbar chargino^-, b tbar chargino^+, g neutralino are comparable. Stops and sbottoms may also be visible. Charginos and neutralinos can be light with the LSP predominantly bino-like. In the second part of the paper we analyze a complete three family model and discuss the quality of the global chi^2 fits and the differences between the third family analysis and the full three family analysis for overlapping observables. We note that the light Higgs in our model couples to matter like the Standard Model Higgs. Any deviation from this would rule out this model., Comment: 27 pages, 11 figs

Talk given at PASCOS 2012, Merida, Mexico describing work in progress in collaboration with Archana Anandakrishnan, Christopher Plumberg and Akin Wingerter., Comment: 10 pages, 6 figures, PASCOS 2012 proceedings

We engineer compact SU(5) Grand Unified Theories in F-theory in which GUT-breaking is achieved by a discrete Wilson line. Because the internal gauge field is flat, these models avoid the high scale threshold corrections associated with hypercharge flux. Along the way, we exemplify the `local-to-global' approach in F-theory model building and demonstrate how the Tate divisor formalism can be used to address several challenges of extending local models to global ones. These include in particular the construction of G-fluxes that extend non-inherited bundles and the engineering of U(1) symmetries. We go beyond chirality computations and determine the precise (charged) massless spectrum, finding exactly three families of quarks and leptons but excessive doublet and/or triplet pairs in the Higgs sector (depending on the example) and vector-like exotics descending from the adjoint of SU(5)_{GUT}. Understanding why vector-like pairs persist in the Higgs sector without an obvious symmetry to protect them may shed light on new solutions to the mu problem in F-theory GUTs., Comment: 95 pages (71 pages + 1 Appendix); v2 references added, minor corrections

We consider a 6-dimensional supersymmetric SU(6) gauge theory and compactify two extra-dimensions on a multiply-connected manifold with non-trivial topology. The SU(6) is broken down to the Standard Model gauge groups in two steps by an orbifold projection (or Wilson line), followed by a Wilson line. The Higgs doublets of the low energy electroweak theory come from a chiral adjoint of SU(6). We thus have gauge-Higgs unification. The three families of the Standard Model can either be located in the 6D bulk or at 4D N=1 supersymmetric fixed points. We calculate the Kaluza-Klein spectrum of states arising as a result of the orbifolding. We also calculate the threshold corrections to the coupling constants due to this tower of states at the lowest compactification scale. We study the regions of parameter space of this model where the threshold corrections are consistent with low energy physics. We find that the couplings receive only logarithmic corrections at all scales. This feature can be attributed to the large N=2 6D SUSY of the underlying model., Comment: Revised version

This paper describes a set of discrete R symmetries which can be used to define the minimal supersymmetric standard model or singlet extensions of it., Comment: Contribution to KMI Inauguration Conference "Quest for the Origin of Particles and the Universe" (KMIIN), 24-26 Nov. 2011, KMI, Nagoya University

We determine the anomaly free discrete R symmetries, consistent with the MSSM, that commute with SU(5) and suppress the $\mu$ parameter and nucleon decay. We show that the order M of such $Z_M^R$ symmetries has to divide 24 and identify 5 viable symmetries. The simplest possibility is a $Z_4^R$ symmetry which commutes with SO(10). We present a string-derived model with this $Z_4^R$ symmetry and the exact MSSM spectrum below the GUT scale; in this model $Z_4^R$ originates from the Lorentz symmetry of compactified dimensions. We extend the discussion to include the singlet extensions of the MSSM and find $Z_4^R$ and $Z_8^R$ are the only possible symmetries capable of solving the $\mu$ problem in the NMSSM. We also show that a singlet extension of the MSSM based on a $Z_{24}^R$ symmetry can provide a simultaneous solution to the $\mu$ and strong CP problem with the axion coupling in the favoured window., Comment: 44+1 pages, 2 figures

The goal of the present review article is to describe the ingredients necessary to find the Standard Model in the string landscape., Comment: 70 pages, 20 figures, this review article will be published in Reports on Progress in Physics

We calculate the weak scale MSSM spectrum starting from a heterotic string theory compactified on an anisotropic orbifold. Supersymmetry breaking is mediated by vector-like exotics that arise naturally in heterotic string theories. The messengers that mediate SUSY breaking come in incomplete GUT multiplets and give rise to non-universal gaugino masses at the GUT scale. Models with non-universal gaugino masses at the GUT scale have the attractive feature of allowing for precision gauge coupling unification at the GUT scale with negligible contributions from threshold corrections near the unification scale. The unique features of the MSSM spectrum are light gluinos and also large mass differences between the lightest and the next-to-lightest neutralinos and charginos which could lead to interesting signatures at the colliders., Comment: 21 pages, 3 figures

Recently it was shown that there is a unique Z_4^R symmetry for the MSSM which allows the Yukawa couplings and dimension five neutrino mass operator, forbids the mu term and commutes with SO(10). This Z_4^R symmetry contains matter parity as a subgroup and forbids dimension four and five proton decay operators. We show how to construct string vacua with discrete R symmetries in general and this symmetry in particular, and present an explicit example which exhibits the exact MSSM spectrum, the Z_4^R symmetry as well as other desired features such as gauge-top unification. We introduce the Hilbert basis method for determining all D-flat configurations and efficient algorithms for identifying field configurations with a desired residual symmetry. These methods are used in an explicit example, in which we describe in detail how to construct a supersymmetric vacuum configuration with the phenomenologically attractive Z_4^R symmetry. At the perturbative level, this is a supersymmetric Minkowski vacuum in which almost all singlet fields (moduli) are fixed., Comment: 26 pages

We consider the possible anomaly free Abelian discrete symmetries of the MSSM that forbid the mu-term at perturbative order. Allowing for anomaly cancellation via the Green-Schwarz mechanism we identify discrete R-symmetries as the only possibility and prove that there is a unique Z_4^R symmetry that commutes with SO(10). We argue that non-perturbative effects will generate a mu-term of electroweak order thus solving the mu-problem. The non-perturbative effects break the Z_4^R symmetry leaving an exact Z_2 matter parity. As a result dimension four baryon- and lepton-number violating operators are absent while, at the non-perturbative level, dimension five baryon- and lepton-number violating operators get induced but are highly suppressed so that the nucleon decay rate is well within present bounds., Comment: 6 pages

We describe a simple and robust mechanism that stabilizes all Kahler moduli in Type IIB orientifold compactifications. This is shown to be possible with just one non-perturbative contribution to the superpotential coming from either a D3-instanton or D7-branes wrapped on an ample divisor. This moduli-stabilization mechanism is similar to and motivated by the one used in the fluxless G_2 compactifications of M-theory. After explaining the general idea, explicit examples of Calabi-Yau orientifolds with one and three Kahler moduli are worked out. We find that the stabilized volumes of all two- and four-cycles as well as the volume of the Calabi-Yau manifold are controlled by a single parameter, namely, the volume of the ample divisor. This feature would dramatically constrain any realistic models of particle physics embedded into such compactifications. Broad consequences for phenomenology are discussed, in particular the dynamical solution to the strong CP-problem within the framework., Comment: RevTeX, 24 pages, 2 tables, 1 figure.

In this paper we discuss the issues of supersymmetry breaking and moduli stabilization within the context of E_8 x E_8 heterotic orbifold constructions and, in particular, we focus on the class of "mini-landscape" models. In the supersymmetric limit, these models admit an effective low energy field theory with a spectrum of states and dimensionless gauge and Yukawa couplings very much like that of the MSSM. These theories contain a non-Abelian hidden gauge sector which generates a non-perturbative superpotential leading to supersymmetry breaking and moduli stabilization. We demonstrate this effect in a simple model which contains many of the features of the more general construction. In addition, we argue that once supersymmetry is broken in a restricted sector of the theory, then all moduli are stabilized by supergravity effects. Finally, we obtain the low energy superparticle spectrum resulting from this simple model., Comment: LaTeX, v2: 57+1 pages, 4 figures, 8 Tables, added references; this version i) discusses volume moduli stabilization with exponentials of both sign (as sometimes mandated by modular invariance); ii) includes the anomalous U(1)_A D-term & the leading Coleman-Weinberg 1-loop correction into the MSSM soft masses to prevent tachyonic results

We discuss the issue of precision gauge unification in the MSSM. We find that a comparably light gluino, as it emerges in certain patterns of soft supersymmetry breaking, can be a key ingredient for ensuring precision gauge unification without relying on the presence of extra particles around the scale of grand unification. In particular, the so-called mirage pattern for gaugino masses can naturally lead to precision gauge unification. There is also an interesting correlation with reduced fine-tuning, due to rather light gluinos., Comment: 14 pages, 3 figures, minor modifications, matches published version

In this talk I review some recent progress in heterotic and F theory model building. I then consider work in progress attempting to find the F theory dual to a class of heterotic orbifold models which come quite close to the MSSM., Comment: 11 pages, 10 figures, plenary talk submitted for the proceedings of SUSY 2009, June 5 - 10, Northeastern University, Boston, MA

In this paper we present a simple extension of the minimal supersymmetric standard model [MSSM] which "naturally" produces the INTEGRAL photon signal. The model can be embedded in an SU(5) grand unified theory [GUT] with gauge mediated SUSY breaking. The new ingredients are the addition of several MSSM singlets/moduli. While the masses of the singlets are at the weak scale, their mass splittings are suppressed by chiral symmetry breaking and naturally lie around an MeV. The decay of the heavier modulino to the lighter one with the associated production of electron - positron pairs explains the INTEGRAL signal. Finally, the detection of diffuse gamma rays from internal bremsstrahlung in the galactic halo would be a suggestive indication of dark matter decays associated with the 511 keV line, and is an unambiguous additional prediction of this model., Comment: 18 pages, 3 figures, 1 table, references added