Search

We compute the energy scales of perturbative unitarity violation in $V_L V_L \to V_L V_L h$ processes and compare them to $V_L V_L \to hhh$ process, where $V_L$ refers to a longitudinal mode of $Z$ or $W$ boson, and $h$ the Higgs boson. Using these energy scales, we determine which process is more sensitive to potential modifications in the Higgs sector at high-energy colliders. Within the Higgs Effective Field Theory (HEFT), we consider the Higgs cubic coupling and other interactions with and without derivatives. Any HEFT interactions predict the perturbative unitarity violation at a finite scale, and in a generic case, the minimalistic process is $2\to 3$ scattering. Our analysis reveals that the energy scales for unitarity violation in $V_L V_L \to V_L V_L h$ and $V_L V_L \to hhh$ processes are similar across all scenarios considered. If the backgrounds are similar, $V_L V_L h$ final states are more feasible because $V_L V_L h$ has higher branching ratios in cleaner decay modes than $hhh$. We also investigate HEFT derivative interactions derived from various UV models. In these cases, both $V_L V_L \to V_L V_L$ and $V_L V_L \to hh$ processes exhibit unitarity violating behavior. We demonstrate that the energy scales for unitarity violation in $V_L V_L$ final states are comparable to or even lower than those in the $hh$ final state., Comment: 28 pages, 3 tables, 7 figures, 5 appendices. v2: Journal version; added references, corrected equations, and minor text changes

An excess in the branching fraction for $B^+ \to K^+ \nu\nu$ recently measured at Belle II may be a hint of new physics. We perform thorough likelihood analyses for different new physics scenarios such as $B \to KX$ with a new invisible particle $X$, or $B\to K\chi\chi$ through a scalar, vector, or tensor current with $\chi$ being a new invisible particle or a neutrino. We find that vector-current 3-body decay with $m_X \simeq 0.6$ GeV - which may be dark matter - is most favored, while 2-body decay with $m_X \simeq 2$ GeV is also competitive. The best-fit branching fractions for the scalar and tensor cases are a few times larger than for the 2-body and vector cases. Past BaBar measurements provide further discrimination, although the best-fit parameters stay similar., Comment: 7 pages, 6 figures, matches published version

The dilaton $\phi$ is a pseudo-Nambu-Goldstone boson associated with the spontaneous breaking of scale invariance in a nearly conformal theory, and couples to the trace of the stress-energy tensor. We analyze experimental constraints on a light dilaton with mass in the MeV-GeV range from rare meson decays. New model-independent inclusive bounds for the $b \to s \phi$ transition largely exclude the parameter space of a light dilaton that could explain the muon $g-2$ anomaly. Despite similarities between a dilaton and a Higgs-portal scalar, the dilaton-photon coupling is enhanced compared to the Higgs-portal scalar due to contributions from loops of the conformal sector. Consequently, the shortened lifetime of the dilaton relaxes bounds from $K \to \pi$ + invisible searches at the NA62 experiment and constraints from the Big Bang Nucleosynthesis. We utilize this fact to search for the dilaton signature at a lepton collider such as the ongoing Belle II experiment. Further, we demonstrate how to extract the CP property of the dilaton using the variation of the differential cross-section of $e^+ e^- \to e^+ e^- \phi$ with the azimuthal angle between the outgoing leptons., Comment: 14 pages, 5 figures

A modified neutrino sector could imprint a signature on precision measurements of the quark sector because many such measurements rely on the semi-leptonic decays of the charged currents. Currently, global fits of the determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements point to a $3\sigma$-level deficit in the first-row CKM unitarity test, commonly referred to as the Cabibbo-angle anomaly. We find that a MeV sterile neutrino that mixes with the electron-type neutrino increases the extracted $|V_{ud}|$, accommodating the Cabibbo-angle anomaly. This MeV sterile neutrino affects the superallowed nuclear $\beta$ decays and neutron decay, but it barely modifies the other measurements of the CKM elements. While various constraints may apply to such a sterile neutrino, we present viable scenarios within an extension of the inverse seesaw model., Comment: 11 pages, 3 figures; v2: references added; v3: matches version published in PRD

While the main goal of the J-PARC KOTO experiment is to measure the rare decay $K_L \to \pi^0 \nu \bar \nu$, the unique setup of KOTO raises the possibility to search for physics beyond the Standard Model, in an attempt to probe parts of the parameter space which are not covered by other experiments. In this paper, we test the possibility of using KOTO to search for heavy QCD axions, or axion-like particles, a well-motivated extension of the Standard Model emerging in a variety of models. In particular, we estimate the sensitivity of the current KOTO setup as well as the KOTO Step-2 for various benchmark scenarios of axion coupling to the Standard Model. We find that KOTO Step-2 can probe new regions in the parameter space, while KOTO with its current form can only reaffirm the existing bounds. The obtained axion datasets are available as an update of the public code of the ALPINIST framework, including implementation of KOTO setups in the simulation, allowing for interpretation of various analyses as searches for axions in custom models., Comment: 9 pages + appendices, 6 figures, ALPINIST code available at https://github.com/jjerhot/ALPINIST/ v2: fix bug in the production from secondary mesons, main conclusions are unchanged

A beam dump experiment can be seamlessly added to the {proposed} International Linear Collider (ILC) program because the high energy electron beam should be dumped after the collision point. The ILC beam dump experiment will provide an excellent opportunity to search for new long-lived particles. Since many of them can be produced by a rare decay of standard model particles, we evaluate spectra of the mesons and $\tau$ lepton at the decay based on the PHITS and PYTHIA8 simulations. As a motivated physics case, we study the projected sensitivity of heavy neutral leptons at the ILC beam dump experiment. The heavy neutral leptons can also be produced via deep inelastic scattering and $Z$ boson decay at the ILC main detector, which we include in the projection. With the multi-track signal, the reach would be greatly extended in mass and coupling, even compared with the other proposed searches., Comment: 23+18 pages, 24 figures; typos fixed; discussions about the background added; Fig. 6 and appendix G added for more information; version published in JHEP

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community., Comment: 356 pages, Large pdf file (40 MB) submitted to Snowmass 2021; v2 references to Snowmass contributions added, additional authors; v3 references added, some updates, additional authors

Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors., Comment: 108 pages, 25 figures, 9 tables, matches the published version

The QCD axion is a well-motivated addition to the standard model to solve the strong $C\!P$ problem. If the axion acquires mass dominantly from a hidden sector, it can be as heavy as $O(1)$ GeV, and the decay constant can be as low as $O(100)$ GeV without running into the axion quality problem. We propose new search strategies for such heavy QCD axions at the Belle II experiment, where the axions are expected to be produced via $B\to K a$. We find that a subsequent decay $a\to 3\pi$ with a displaced vertex leads to a unique signal with essentially no background, and that a dedicated search can explore the range $O(1$-$10)$ TeV of decay-constant values. We also show that $a\to \gamma\gamma$ can cover a significant portion of currently unexplored region of $150 \lesssim m_a \lesssim 500$ MeV., Comment: 7 pages, 4 figures; Version accepted for publication in PRD Letter, including experimental results published after version-1 that imply new limits on the axion parameters

With the establishment and maturation of the experimental programs searching for new physics with sizeable couplings at the LHC, there is an increasing interest in the broader particle and astrophysics community for exploring the physics of light and feebly-interacting particles as a paradigm complementary to a New Physics sector at the TeV scale and beyond. FIPs 2020 has been the first workshop fully dedicated to the physics of feebly-interacting particles and was held virtually from 31 August to 4 September 2020. The workshop has gathered together experts from collider, beam dump, fixed target experiments, as well as from astrophysics, axions/ALPs searches, current/future neutrino experiments, and dark matter direct detection communities to discuss progress in experimental searches and underlying theory models for FIPs physics, and to enhance the cross-fertilisation across different fields. FIPs 2020 has been complemented by the topical workshop "Physics Beyond Colliders meets theory", held at CERN from 7 June to 9 June 2020. This document presents the summary of the talks presented at the workshops and the outcome of the subsequent discussions held immediately after. It aims to provide a clear picture of this blooming field and proposes a few recommendations for the next round of experimental results., Comment: 240 pages, 71 figures (version published on EPJC)

We study a "heavy" QCD axion whose coupling to the standard model is dominated by $a G \widetilde{G}$ but with $m_a \gg m_\pi f_\pi / f_a$. This is well motivated as it can solve the strong CP problem while evading the axion quality problem. It also poses interesting challenges for its experimental search due to its suppressed couplings to photons and leptons. Such axion with mass around a GeV is kinematically inaccessible or poorly constrained by most experimental probes except B-factories. We study $B \to K a$ transitions as a powerful probe of the heavy QCD axion by performing necessary 2-loop calculations for the first time, together with some improvement on the existing analysis strategy. We find some of the existing limits are enhanced by at least an order of magnitude. We also demonstrate that the bounds are robust against unknown UV physics. For forthcoming data sets of the Belle II experiment, we provide a projection that $f_a$ of a few TeV is within its future reach, which is relevant to the quality problem., Comment: 9 pages, 4 figures; Two Typos are corrected; one in equation (B7) and the second in the y-axis scale of Fig. 3. No conclusions and final results changed

Triple heavy vector boson production, $p p \to VVV$ $(V = W, Z)$, has recently been observed for the first time. We propose that precision measurements of this process provide an excellent probe of the first generation light quark Yukawa couplings. Modified quark interactions with the off-shell Higgs in this process lead to a rapid growth of the partonic cross sections with energy, which manifests in an enhanced $p_T$ distribution of the final state leptons and quarks. We quantify this effect and estimate the present and future 2$\sigma$ sensitivity to the up, down, and strange Yukawas. In particular, we find that HL-LHC can reach $\mathcal{O}(400)$ sensitivity to the down Yukawa relative to the Standard Model value, improving the current sensitivity in this process by a factor of $10$, and which can be further improved to $\mathcal{O}(30)$ at FCC-hh. This is competitive with and complementary to constraints from global fits and other on-shell probes of the first generation Yukawas. The triboson sensitivity at HL-LHC corresponds to probing dimension-6 SMEFT operators suppressed by an $\mathcal{O}(1)$ TeV scale, similarly to other LHC Higgs probes., Comment: 22 pages, 6 figures

Solar interpretations of the recent XENON1T excess events, such as axion or dark photon emissions from the sun, are thought to be at odds with stellar cooling bounds from the horizontal branch stars and red giants. We propose a simple effective field theory of a dark photon in which a $Z_2$ symmetry forbids a single dark photon emission in the dense stars, thereby evading the cooling bounds, while the $Z_2$ is spontaneously broken in the vacuum and sun, thereby explaining the XENON1T excess. The scalar responsible for the $Z_2$ breaking has an extremely flat potential, but the flatness can be maintained under quantum corrections. The UV completion of the EFT generally requires the existence of new electrically charged particles with sub-TeV masses with $O(1)$ couplings to the dark photon, offering the opportunity to test the scenario further and opening a new window into the dark sector in laboratory experiments., Comment: 9 pages, 4 figures; Fifth force, equivalence principle constraints and some references are added. The main conclusions are unchanged

The two kaon factories, KOTO and NA62, are at the cutting edge of the intensity frontier, with an unprecedented numbers of long lived and charged Kaons, ~ 10^{13}, being measured and analyzed. These experiments have currently a unique opportunity to search for dark sectors. In this paper, we demonstrate that searches done at KOTO and NA62 are complementary, both probing uncharted territories. We consider two qualitatively different physics cases. In the first, we analyze models of axion-like-particles (ALP) which couple to gluons or electroweak gauge bosons. In the second, we introduce a model based on an approximate strange flavor symmetry that leads to a strong violation of the Grossman-Nir bound. For the first scenario, we design a new search strategy for the KOTO experiment, K_L -> pi^0 a -> 4 gamma . Its expected sensitivity on the branching ratio is at the level of 10^{-9}. This demonstrates the great potential of KOTO as a discovery machine. In addition, we revisit other bounds on ALPs from Kaon factories, highlighting the main sources of theoretical uncertainty, and collider experiments, and show new projections. For the second scenario, we show that the model may be compatible with the preliminary analysis of the KOTO-data that shows a hint for New Physics., Comment: 32 pages, 14 figures, and appendices

The KOTO experiment recently reported four candidate events in the signal region of $K_L\to \pi^0 \nu\bar\nu$ search, where the standard model only expects $0.10\pm 0.02$ events. If confirmed, this requires physics beyond the standard model to enhance the signal. We examine various new physics interpretations of the result including these: (1) heavy new physics boosting the standard model signal, (2) reinterpretation of "$\nu\bar{\nu}$" as a new light long-lived particle, or (3) reinterpretation of the whole signal as the production of a new light long-lived particle at the fixed target. We study the above explanations in the context of a generalized new physics Grossman-Nir bound coming from the $K^+ \to \pi^+\nu\bar{\nu}$ decay, bounded by data from the E949 and the NA62 experiments., Comment: 7 pages, 3 figures; v2: references added, simulation refined; v3: matches version published in PRL

Rare kaon decays are excellent probes of light, new weakly-coupled particles. If such particles $X$ couple preferentially to muons, they can be produced in $K\to \mu \nu X$ decays. In this letter we evaluate the future sensitivity for this process at NA62 assuming $X$ decays either invisibly or to di-muons. Our main physics target is the parameter space that resolves the $(g-2)_\mu$ anomaly, where $X$ is a gauged $L_\mu-L_\tau$ vector or a muon-philic scalar. The same parameter space can also accommodate dark matter freeze out or reduce the tension between cosmological and local measurements of $H_0$ if the new force decays to dark matter or neutrinos, respectively. We show that for invisible $X$ decays, a dedicated single muon trigger analysis at NA62 could probe much of the remaining $(g-2)_\mu$ favored parameter space. Alternatively, if $X$ decays to muons, NA62 can perform a di-muon resonance search in $K\to 3 \mu \nu$ events and greatly improve existing coverage for this process. Independently of its sensitivity to new particles, we find that NA62 is also sensitive to the Standard Model predicted rate for $K \to 3\mu \nu$, which has never been measured., Comment: 6 + 4 pages; v2 small change in limits, conclusions unchanged, matches version published in PRL

We assess the impact of searches at flavor factories for new neutral resonances that couple to both photons and gluons. These are well motivated by "heavy axion" solutions of the strong CP problem and by frameworks addressing both Dark Matter and the Higgs hierarchy problem. We use LHCb public diphoton data around the Bs mass to derive the current best limit on these resonances for masses between 4.9 and 6.3 GeV. We estimate that a future LHCb dedicated search would test an axion decay constant of O(TeV) for axion masses in the few-to-tens of GeV, being fully complementary to the low mass ATLAS and CMS searches. We also derive the impact of BABAR searches based on Upsilon decays and the future Belle-II reach., Comment: 13 pages, 5 figures. v2: reference added, Upsilon decay corrected in equation (5) and in figures, conclusions unchanged

We derive a new bound on diphoton resonances using inclusive diphoton cross section measurements at the LHC, in the so-far poorly constrained mass range between the Upsilon and the SM Higgs. This bound sets the current best limit on axion-like particles that couple to gluons and photons, for masses between 10 and 65 GeV. We also estimate indicative sensitivities of a dedicated diphoton LHC search in the same mass region, at 7, 8 and 14 TeV. As a byproduct of our analysis, we comment on the axion-like particle interpretation of the CMS excesses in low-mass dijet and diphoton searches., Comment: 7 pages + appendices, 5 figures, 2 tables. v2: discussion improved, new bound derived also from Tevatron, conclusions unchanged. v3: matches PLB version

The cosmological relaxation of the electroweak scale has been proposed as a mechanism to address the hierarchy problem of the Standard Model. A field, the relaxion, rolls down its potential and, in doing so, scans the squared mass parameter of the Higgs, relaxing it to a parametrically small value. In this work, we promote the relaxion to an inflaton. We couple it to Abelian gauge bosons, thereby introducing the necessary dissipation mechanism which slows down the field in the last stages. We describe a novel reheating mechanism, which relies on the gauge-boson production leading to strong electromagnetic fields, and proceeds via the vacuum production of electron-positron pairs through the Schwinger effect. We refer to this mechanism as Schwinger reheating. We discuss the cosmological dynamics of the model and the phenomenological constraints from CMB and other experiments. We find that a cutoff close to the Planck scale may be achieved. In its minimal form, the model does not generate sufficient curvature perturbations and additional ingredients, such as a curvaton field, are needed., Comment: 39 pages, 3 figures, appendices D and E added, published in JHEP

We present an effective model where the inflaton is a relaxion that scans the Higgs mass and sets it at the weak scale. The dynamics consist of a long epoch in which inflation is due to the shallow slope of the potential, followed by a few number of e-folds where slow-roll is maintained thanks to dissipation via non-perturbative gauge-boson production. The same gauge bosons give rise to a strong electric field that triggers the production of electron-positron pairs via the Schwinger mechanism. The subsequent thermalization of these particles provides a novel mechanism of reheating. The relaxation of the Higgs mass occurs after reheating, when the inflaton/relaxion stops on a local minimum of the potential. We argue that this scenario may evade phenomenological and astrophysical bounds while allowing for the cutoff of the effective model to be close to the Planck scale. This framework provides an intriguing connection between inflation and the hierarchy problem., Comment: 5 pages, 1 figure

In his 1977 paper on vacuum decay in field theory: The Fate of the False Vacuum, Coleman considered the problem of a single scalar field and assumed that the minimum action tunnelling field configuration, the bounce, is invariant under O(4) rotations in Euclidean space. A proof of the O(4) invariance of the bounce was provided later by Coleman, Glaser, and Martin (CGM), who extended the proof to $N>2$ Euclidean dimensions but, again, restricted non-trivially to a single scalar field. As far as we know a proof of O($N$) invariance of the bounce for the tunnelling problem with multiple scalar fields has not been reported, even though it was assumed in many works since, being of phenomenological interest. We make progress towards closing this gap. Following CGM we define the reduced problem of finding a field configuration minimizing the kinetic energy at fixed potential energy. Given a solution of the reduced problem, the minimum action bounce can always be obtained from it by means of a scale transformation. We show that if a solution of the reduced problem exists, then it and the minimum action bounce derived from it are indeed O($N$) symmetric., Comment: 10 pages, 1 figure: v3: match journal version

We consider the absorption by bound electrons of dark matter in the form of dark photons and axion-like particles, as well as of dark photons from the Sun, in current and next-generation direct detection experiments. Experiments sensitive to electron recoils can detect such particles with masses between a few eV to more than 10 keV. For dark photon dark matter, we update a previous bound based on XENON10 data and derive new bounds based on data from XENON100 and CDMSlite. We find these experiments to disfavor previously allowed parameter space. Moreover, we derive sensitivity projections for SuperCDMS at SNOLAB for silicon and germanium targets, as well as for various possible experiments with scintillating targets (cesium iodide, sodium iodide, and gallium arsenide). The projected sensitivity can probe large new regions of parameter space. For axion-like particles, the same current direction detection data improves on previously known direct-detection constraints but does not bound new parameter space beyond known stellar cooling bounds. However, projected sensitivities of the upcoming SuperCDMS SNOLAB using germanium can go beyond these and even probe parameter space consistent with possible hints from the white dwarf luminosity function. We find similar results for dark photons from the sun. For all cases, direct-detection experiments can have unprecedented sensitivity to dark-sector particles., Comment: 18 pages, 5 figures, Figs. 3 and 4 fixed, appendices added

A quantitative discussion on the future prospects of the 750 GeV resonance at the LHC experiment is given using a simple effective field theory analysis. The relative size of two effective operators relevant to diphoton decays can be probed by ratios of diboson signals in a robust way. We obtain the future sensitivities of $Z\gamma $, $ZZ$ and $WW$ resonance searches at the high luminosity LHC, rescaling from the current sensitivities at $\sqrt{s}=13$ TeV. Then, we show that a large fraction of parameter space in the effective field theory will be covered with 300 fb$^{-1}$ and almost the whole parameter space will be tested with 3000 fb$^{-1}$. This discussion is independent of production processes, other decay modes and total decay width., Comment: version published, reference added, 4 pages, 3 figures

The chiral anomaly provides a smoking-gun evidence of a new confining gauge theory. Motivated by a reported event excess in a diphoton invariant mass distribution at the LHC, we discuss a scenario that a pseudo-Nambu-Goldstone (pNG) boson of a new QCD-like theory is produced by gluon fusion and decays into a pair of the standard model gauge bosons. Despite the strong dynamics, the production cross section and the decay widths are determined by anomaly matching condition. The excess can be explained by the pNG boson with mass of around 750 GeV. The model also predicts exotic hadrons such as a color octet scalar and baryons. Some of them are within the reach of the LHC experiment., Comment: 7 pages, 2 figures, typos fixed, figure 1 added, and journal version

Supersymmetry is a prime candidate for physics beyond the Standard Model because low-energy supersymmetry stabilizes the Higgs mass avoiding fine-tuning and leads to natural electroweak symmetry breaking. However, searches at the Large Hadron Collider (LHC) for supersymmetric particles have not found any signal and give strong limits on mass of gluino and squark. Also, the observed Higgs mass of 125 GeV is not easily accommodated in the minimal supersymmetric Standard Model (MSSM) where one has to rely on the radiative corrections to boost the Higgs mass accompanied with fine-tuning. I study aspects of supersymmetry in light of these LHC results. In this thesis, I focus on the Compact Supersymmetry model based on arXiv:1206.4993 and the Dirac Next-to-MSSM based on arXiv:1308.0792 and investigate them in more detail., Comment: 144 pages, 49 figures, 9 tables, Ph. D thesis submitted in March, 2014

The current LHC results make weak scale supersymmetry difficult due to relatively heavy mass of the discovered Higgs boson and the null results of new particle searches. Geometrical supersymmetry breaking from extra dimensions, Scherk-Schwarz mechanism, is possible to accommodate such situations. A concrete example, the Compact Supersymmetry model, has a compressed spectrum ameliorating the LHC bounds and large mixing in the top and scalar top quark sector with $|A_t|\sim 2m_{\tilde{t}}$ which radiatively raises the Higgs mass. While the zero mode contribution of the model has been considered, in this paper we calculate the Kaluza-Klein tower effect to the Higgs mass. Although such contributions are naively expected to be as small as a percent level for 10 TeV Kaluza-Klein modes, we find the effect significantly enhances the radiative correction to the Higgs quartic coupling by from 10 to 50 %. This is mainly because the top quark wave function is pushed out from the brane, which makes the top mass depend on higher powers in the Higgs field. As a result the Higgs mass is enhanced up to 15 GeV from the previous calculation. We also show the whole parameter space is testable at the LHC run II., Comment: 30 pages, 8 figures, appendix C added, conclusion unchanged, journal version

We discuss the prospects to probe the light-quark Yukawa couplings to the Higgs boson. The Higgs coupling to the charm quark can be probed both via inclusive and exclusive approaches. On the inclusive frontier, we use our recently proposed method together with published experimental studies for the sensitivity of the Higgs coupling to bottom quarks to find that the high-luminosity LHC can be sensitive to modifications of the charm Yukawa of the order of a few times its standard model (SM) value. We also present a preliminary study of this mode for a 100 TeV hadronic machine (with similar luminosity) and find that the bound can be further improved, possibly within the reach of the expected signal in the SM. On the exclusive frontier, we use the recent ATLAS search for charmonia and photon final state. This study yields the first measurement of the background relevant to these modes. Using this background measurement we project that at the high-luminosity LHC, unless the analysis strategy is changed, the sensitivity of the exclusive final state to the charm Yukawa to the charm Yukawa will be rather poor, of the order of 50 times the SM coupling. We then use a Monte-Carlo study to rescale the above backgrounds to the h->phi gamma case and obtain a much weaker sensitivity to the strange Yukawa, of order of 3000 times the SM value. We briefly speculate what would be required to improve the prospects of the exclusive modes., Comment: 16 pages, 8 figures, journal version, updated references and minor corrections, conclusions unchanged

We introduce four different types of data-driven analyses with different level of robustness that constrain the size of the Higgs-charm Yukawa coupling: (i) recasting the vector-boson associated, Vh, analyses that search for bottom-pair final state. We use this mode to directly and model independently constrain the Higgs to charm coupling, y_c/y_c^{SM} < 234; (ii) the direct measurement of the total width, y_c/y_c^{SM} < 120-140; (iii) the search to h -> J/\psi\gamma, y_c/y_c^{SM} < 220; (iv) a global fit to the Higgs signal strengths, y_c/y_c^{SM} < 6.2. A comparison with t\bar{t}h data allows us to show that current data eliminates the possibility that the Higgs couples to quarks in a universal way, as is consistent with the Standard Model (SM) prediction. Finally, we demonstrate how the experimental collaborations can further improve our direct bound by roughly an order of magnitude by charm-tagging, as already used in new physics searches., Comment: 8 pages, 6 figures

We calculate all gauge invariant Barr-Zee type contributions to fermionic electric dipole moments (EDMs) in the two-Higgs doublet models (2HDM) with softly broken Z2 symmetry. We start by studying the tensor structure of h to VV' part in the Barr-Zee diagrams, and we calculate the effective couplings in a gauge invariant way by using the pinch technique. Then we calculate all Barr-Zee diagrams relevant for electron and neutron EDMs. We make bounds on the parameter space in type-I, type-II, type-X, and type-Y 2HDMs. The electron and neutron EDMs are complementary to each other in discrimination of the 2HDMs. Type-II and type-X 2HDMs are strongly constrained by recent ACME experiment's result, and future experiments of electron and neutron EDMs may search O(10) TeV physics., Comment: 36 pages, 20 figures, 3 tables; v2: published version; v3: typos corrected

The Higgs mass implies fine-tuning for minimal theories of weak scale supersymmetry (SUSY). Non-decoupling effects can boost the Higgs mass when new states interact with the Higgs, but new sources of SUSY breaking that accompany such extensions threaten naturalness. We show that two singlets with a Dirac mass can increase the Higgs mass while maintaining naturalness in the presence of large SUSY breaking in the singlet sector. We explore the modified Higgs phenomenology of this scenario, which we call the "Dirac NMSSM.", Comment: Version published in PRL, plus two additional figures. 6 pages, 4 figures

The discovery of the Higgs boson with a mass of about 125 GeV intimates us a possibility of a high-scale supersymmetry (SUSY) breaking model, where a sfermion mass scale is much higher than the electroweak scale. Although a general SUSY standard model can contribute to the low-energy flavor and/or CP-violating processes, the high-scale SUSY breaking model provides smaller signatures and therefore are less constrained, even in the presence of large flavor/CP violations of sfermions. However, a manner of gluino decay directly reflects the squark flavor structure and provides us a clue for the sfermion flavor structure. In this paper, we study the gluino decay in detail and discuss the interplay with the gluino decay and low-energy flavor and CP observation., Comment: 31 pages, 9 figures

We study the diphoton signal of the Higgs boson in gauge mediated supersymmetry breaking models, which can explain both the Higgs boson mass of around 125 GeV and the result of the muon g-2 experiment. We consider two possible extensions of gauge mediation models: inclusion of vector-like matters, and a mixing between a messenger and the up-type Higgs. The large left-right mixing of staus is induced in both scenarios, resulting in the enhanced diphoton signal. We include a constraint from a charge breaking minimum, which is severe for the large left-right mixing of staus. The branching fraction of h to gamma gamma can be about 40 percent larger than that of the Standard Model Higgs boson, in the region of parameter space where the Higgs boson mass of around 125 GeV and the muon g-2 are explained., Comment: 13 pages, 4 figures; Figures updated, taking into account results in new version (v2) of 1011.0260; references added

A supersymmetric standard model with heavier scalar supersymmetric particles has many attractive features. If the scalar mass scale is O(10 - 10^4) TeV, the standard model like Higgs boson with mass around 125 GeV, which is strongly favored by the LHC experiment, can be realized. However, in this scenario the scalar particles are too heavy to be produced at the LHC. In addition, if the scalar mass is much less than O(10^4) TeV, the lifetime of the gluino is too short to be measured. Therefore, it is hard to probe the scalar particles at a collider. However, a detailed study of the gluino decay reveals that two body decay of the gluino carries important information on the scalar scale. In this paper, we propose a test of this scenario by measuring the decay pattern of the gluino at the LHC., Comment: 29 pages, 9 figures; version published in JHEP

Supersymmetry broken geometrically in extra dimensions naturally leads to a nearly degenerate spectrum for superparticles, ameliorating the bounds from the current searches at the LHC. We present a minimal such model with a single extra dimension, and show that it leads to viable phenomenology despite the fact that it essentially has two less free parameters than the conventional CMSSM. The theory does not suffer from the supersymmetric flavor or CP problem because of universality of geometric breaking, and automatically yields near-maximal mixing in the scalar top sector with |A_t| ~ 2 m_{\tilde{t}} to boost the Higgs boson mass. Despite the rather constrained structure, the theory is less fine-tuned than many supersymmetric models., Comment: 6 pages 5 figures, version accepted for publication in PRD. SLHA files are available at http://www-theory.lbl.gov/~shirai/compactSUSY.php

Vector-like quarks are introduced in various new physics models beyond the standard model (SM) at the TeV scale. We especially consider the case that the quark is singlet (triplet) under the SU(2)$_L$ (SU(3)$_c$) gauge group and couples only to the third generation quarks of the SM. The vector-like quark of this kind is often called a top partner. The top partoner $t_p$ decays into $bW, tZ$ and $th$. In the ATLAS and CMS collaborations, the top partner has been searched in the final states of $bW$ and $tZ$, while the search based on the decay mode $t_p\to th$ has not been started yet. However, the decay into $th$ is important since it is significantly enhanced if some strong dynamics exists in the TeV scale. In the presence of a light higgs boson, the decay mode $t_p\to th$ followed by $h\to b\bar{b}$ produces three bottom quarks. We study the sensitivity for the top partner using multi-b-jet events at the 8 TeV run of the LHC experiment. The multi-b-jet eventss turn out to play a complementary role to the existing $t_p\rightarrow bW$ and $tZ$ searches by the ATLAS and CMS collaborations., Comment: 26 pages, 9 figures, 10 Tables

In the framework of the little higgs scenario, coupling constants of several interactions are related to each other to guarantee the stability of the higgs boson mass at one-loop level. This relation is called the little higgs mechanism. We discuss how accurately the relation can be tested at future e+e- colliders, with especially focusing on the top sector of the scenario using a method of effective lagrangian. In order to test the mechanism at the top sector, it is important to measure the Yukawa coupling of the top partner. We consider higgs associated production and threshold production of the top partner, and find that the mechanism can be tested precisely using the associate production when the center of mass energy is large enough. The threshold production also allows us to test it even if the center mass energy is not so large., Comment: 22 pages, 5 figures, 2 tables ; v2 minor corrections

We study the discovery potential of the Minimal Universal Extra Dimension model (MUED) and improve it utilizing the multijet + lepton mode at the LHC. Since the MUED has a nearly degenerate spectrum, most events only have soft jets and small Emiss. The signature is challenging to search. We apply MT2 for the event selection and set the invisible particle mass of MT2 (test mass) to zero. The test mass is much smaller than the invisible particle mass of MUED. In that case, MT2 of the signal can be large depending on Up-Stream Radiations (USR) which includes initial state radiations (ISR). On the other hand, MT2 of the background is mainly below the top quark mass. Hence, the signal is extracted from the background in the high MT2 region. Since we use the leading jets for MT2, there is a combinatorics effect. We found the effect also enhances the signal to background ratio for high MT2. We perform a detailed simulation with the Matrix Element correction to the QCD radiations. The discovery potential of the MUED is improved by the MT2 cut, and especially, the improvement is significant for the most degenerate parameter we consider, {\Lambda}R = 10., Comment: 22 pages, 6 figures