Search

Boosted dark matter constitutes a small fraction of the total dark matter in the universe, with mass ranging from eV to MeV and often exhibiting (semi)relativistic velocity. Hence the likelihood of detecting boosted dark matter in earth-based direct detection experiments is relatively high. There is more than one explanation for the origin of the boosted dark matter(subdominant) including the two-component dark matter models where the heavier dark matter species(dominant) annihilates to nearly monoenergetic light dark matter particles in the galactic halo. If the dominant dark matter species is heavier (MeV-GeV), the subdominant light dark matter achieves very high velocity. These boosted dark matter particles suffer from elastic scattering with electrons and nuclei while crossing the atmosphere and the earth's crust before reaching underground experiments and hence the kinetic energy of the dark matter is attenuated. In the two component dark matter scenario, we show that the boost of the dark matter, kinetic energy and its attenuation highly depend on the dark matter masses. We perform a detailed study of the attenuation of boosted dark matter as a function of the DM-nucleus (without/with form factor) and DM-electron cross sections. For a 10 MeV dark matter with boost $\sim$ 10-100, the effect of DM-electron scattering is found to be severe than the DM-nucleus scattering (with form factor) for scattering cross sections $\sim 10^{-29}$cm$^2$. We also found that the attenuation of the kinetic energy results in a shift in the peak position of the boosted dark matter flux., Comment: 17 pages

We study the two-component boosted dark matter (DM) scenario in a neutrinophilic two-Higgs doublet model ($\nu 2$HDM), which comprises of one extra Higgs doublet with a MeV scale CP-even scalar H. This model is extended with a light ($\sim 10$~MeV) singlet scalar DM $\phi_3$, which is stabilized under the existing $Z_2$ symmetry and can only effectively annihilate through scalar $H$. As the presence of a light H modify the oblique parameters to put tight constraints on the model, introduction of vectorlike leptons (VLL) can potentially salvage the issue. These additional vector-like doublet $N$ and one vector-like singlet $\chi$ are also stabilized through the $Z_2$ symmetry. The lightest vectorlike mass eigenstate $\chi_1$ ($ \sim 100$ GeV) can be the potential second DM component of the model. Individual scalar and fermionic DM candidates have Higgs/Z mediated annihilation, restricting the fermion DM in a narrow mass region while a somewhat broader mass region is allowed for the scalar DM. In a coupled scenario, light DM $\phi_3$ gets its boost from the $\chi_1$ annihilation while the fermionic DM opens up new annihilation channel $\chi_1 \chi_1 \to \phi_3 \phi_3$: decreases the relic density. This paves way for more fermionic DM mass with under-abundant relic, a region of [35-60] GeV compared to a smaller [40-50] GeV window for the single component fermion DM. On the other hand, the $\phi_3$ resonant annihilation gets diluted due to boosting effects in kinematics, which increases the DM relic leading to a smaller allowed region. To achieve an under-abundant relic, the total DM relic will be dominated by the $\chi_1$ contribution. While there is a region with $\phi_3$ contribution dominating the total DM, the combined relic becomes over-abundant. Therefore, a sub-dominant ($\sim 5 \%$) boosted scalar is the most favorable light DM candidate to be probed for detection., Comment: 29 pages, 10 figures, 5 tables

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10~TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work., Comment: 118 pages, 103 figures

The Higgs mass is not protected by any symmetry in the Standard Model. Hence, the self-energy corrections to the Higgs mass become large due to the quadratic divergence terms. Veltman condition (V.C.) ensures that the coefficient of the quadratic divergent term either vanishes or becomes negligible. The non-observation of new physics has pushed the new physics scale to be larger than 1 TeV, making it impossible to satisfy the Veltman condition in the Standard Model without very large fine-tuning. Many attempts are made to satisfy the V.C. in Beyond Standard Model theories, but the V.C. is hard to achieve at a very large scale ($\Lambda$). Alternatively, it is possible that the new physics appears much above the Electroweak scale, and the effect of the new physics is observed in terms of the Wilson coefficients of the Standard Model Effective Field Theory (SMEFT) operators. The V.C. can be addressed in the SMEFT framework. In this paper, some specific new physics scenarios are considered at a very large scale. Below that scale, the effect of the new physics is observed as Beyond Standard Model Effective Field Theory (BSM-EFT). We particularly study the type-II seesaw model with the complex scalar triplet ($Y=1$) in the context of V.C. We found that this particular model is the minimal model to generate all SMEFT operators that appear in V.C. and satisfies V.C. We also examine the model parameter dependence of the Wilson coefficients in detail and show how the cancellation of the Wilson coefficients is highly dependent on some specific values of the model parameters., Comment: 14 pages, 3 Figures

It is a challenge for the theoretical particle physicists to perform the phenomenology of the Beyond Standard Model (BSM) theories using advanced simulations which can mimic the experimental environment at the colliders as closely as possible. In collider phenomenology jet substructure is a concept that is used frequently to analyse the properties of the jets, characterised as a cluster of hadrons, which is often the end result of particle collisions at the colliders, such as Large Hadron Collider (LHC). A vast literature on jet substructure exists both from the theory and experimental point of view. But, even with the knowledge of Quantum Chromodynamics (QCD), it is hard to cope up with the vastness of the applicability of the subject for a new researcher in this field. In this review, an attempt has been made to bridge the gap between the concept of jet substructure and its application in the collider phenomenology. However, for detailed understanding, one should look at the references., Comment: Review Article, 12 pages, 1 figure

A pseudo-Nambu Goldstone Boson (pNGB) arising from the breaking of a global symmetry ($G\rightarrow H$) can be one of the most promising candidates for the quintessence model, to explain the late-time acceleration of our universe. Motivated from the Composite Higgs scenario, we have investigated the case where the pNGB associated with $SO(N)/ SO(N-1)$ develops a potential through its couplings with the particles that do not form the complete representations of $G$. The Coleman Weinberg (CW) potential is generated via the external particles in the loop which are linked with the strongly interacting dynamics and can be computed predicatively. The model of Dark Energy (DE) is tested against several latest cosmological observations such as supernovae data of Pantheon, Baryon Acoustic Oscillation (BAO), Redshift-space distortion (RSD) data, etc. We have found that the fit prefers the sub-Planckian value of the pNGB field decay constant. Moreover, we have found that the model predicts cosmological parameters well within the allowed range of the observation and thus gives a well-motivated model of quintessence., Comment: 14 pages, 4 figures, 1 table

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

In the path towards a muon collider with center of mass energy of 10 TeV or more, a stage at 3 TeV emerges as an appealing option. Reviewing the physics potential of such muon collider is the main purpose of this document. In order to outline the progression of the physics performances across the stages, a few sensitivity projections for higher energy are also presented. There are many opportunities for probing new physics at a 3 TeV muon collider. Some of them are in common with the extensively documented physics case of the CLIC 3 TeV energy stage, and include measuring the Higgs trilinear coupling and testing the possible composite nature of the Higgs boson and of the top quark at the 20 TeV scale. Other opportunities are unique of a 3 TeV muon collider, and stem from the fact that muons are collided rather than electrons. This is exemplified by studying the potential to explore the microscopic origin of the current $g$-2 and $B$-physics anomalies, which are both related with muons., Comment: 73 pages, 28 figures; Contribution to Snowmass 2021

Large fermionic multiplets appear in different extensions of the Standard Model (SM), which are essential to predict small neutrino masses, relic abundance of the dark matter (DM) and the measured value of muon anomalous magnetic moment (muon (g-2)). Models containing quintuplet of fermions ($\Sigma$), along with other scalar multiplets, can address recent anomalies in the flavor sector while satisfying the constraints from the electroweak physics. In standard scenarios, the exotic fermions couple with the SM particles directly and there exists a strong limit on their masses from collider experiments such as the Large Hadron Collider (LHC). In this paper, we choose a particular scenario where the quintuplet fermions are heavier than the scalars, which is naturally motivated from the muon (g-2) data. A unique nature of these models is that they predict non-standard signatures at the colliders as the quintuplet fermions decay via the scalars once produced at the colliders. We study these non-standard interactions and provide alternative search strategies for these exotic fermions at the LHC and future linear colliders (such as $e^+e^-$ colliders). We also discuss their exclusion and discovery limits. For the doubly charged quintuplet fermion ($\Sigma^{\pm\pm}$), discovery is possible with 5$\sigma$ significance at integrated luminosity of 3000 fb$^{-1}$ at 14 TeV LHC if $M_\Sigma\leq 980$ GeV. For the singly charged quintuplet fermion ($\Sigma^\pm$), the discovery is challenging at LHC but there might be a possibility of 5 $\sigma$ discovery with 1000 fb$^{-1}$ luminosity at $e^+e^-$ collider for $M_\Sigma\leq 700$ GeV., Comment: 21 pages, 12 figures, 6 tables

Vectorlike quarks have been shown to resolve certain long-standing discrepancies pertaining to the bottom sector. We investigate, here, the prospects of identifying the existence of a topless vectorlike doublet $(B,~Y)$, as is preferred by the electroweak precision measurements. Concentrating on single production, $viz.$ $B \bar b$ with $B \to b + Z/H$ subsequently, we find that the fully hadronic decay-channel is susceptible to discovery provided jet substructure observables are used. At the 13 TeV LHC with an integrated luminosity of 300 fb$^{-1}$, a modest value of the chromomagnetic transition moments allows for the exclusion of $M \lesssim 1.8(2.2)$ TeV in the $Z$ and $H$ channels respectively.

Hints of flavor violation at both charged and neutral current decays of mesons have been observed in experiments such as LHCb, Belle, and BaBar. The anomalies in the result can be addressed in the effective field theory (EFT) framework. The effective operators predict different beyond standard model (BSM) signatures and the four point interaction vertices can be probed at Large Hadron Collider (LHC). In this context, the discovery projection of two opposite sign leptons and a $b$-jet signature is studied in this paper at 13 TeV LHC., Comment: 5 pages, 2 figures, Contribution to proceedings of XXIII DAE-BRNS HEP Symposium 2018, Dec. 10-14, 2018, Chennai, India

The low energy effective theory ($\sim$ TeV) of the little-Higgs model with $SU(6)/Sp(6)$, as proposed by Low, Skiba and Smith (LSS), exhibits a two-Higgs doublet model (2HDM) structure. The symmetry dictates interesting Yukawa patterns, translating to non-trivial fermion couplings with both of the Higgs doublets. The couplings of the scalars with the fermions can induce flavor changing neutral currents (FCNC), which get constraints from flavor physics observables such as BR$(B\rightarrow X_s\gamma)$, $B_s - \bar{B}_s$ mixing etc. The precision measurement of $Z b \bar{b}$ vertex, the top and Higgs mass along with other Higgs coupling measurements at the Large Hadron Collider (LHC) also enforce severe restrictions on the LSS model. Direct LHC search results of beyond the Standard Model (BSM) particles also impose bounds on the masses. We probe the LSS model in view of the above constraints through a random scan in the multi-dimensional parameter space. We observe, on contrary to the general 2HDM scenario, the emergent 2HDM from the LSS model is less constrained from the flavor data and the $Z b \bar{b}$ measurement but is severely constrained form the electroweak (EW) searches at the LHC. From the flavor data and $Z b \bar{b}$, we find that the charged Higgs mass is relaxed with $\tan\beta$ being restricted to $0.5-5$, whereas the charged Higgs mass is pushed to larger than 1 TeV along with $\tan\beta$ being further restricted to $< 3$ when the LHC bounds are incorporated., Comment: 23 pages, 3 figures, minor changes

We consider a model with multi-charged particles including vector-like fermions and a charged scalar under a local $U(1)_{\mu - \tau}$ symmetry. We search for allowed parameter region explaining muon anomalous magnetic moment (muon $g-2$) and $b \to s \ell^+ \ell^-$ anomalies, satisfying constraints from the lepton flavor violations, $Z$ boson decays, meson anti-meson mixing and collider experiments. Carrying out numerical analysis, we explore the typical size of the muon $g-2$ and Wilson coefficients to explain $b \to s \ell^+ \ell^-$ anomalies in our model when all other experimental constraints are satisfied. We then discuss the collider physics of the multicharged vectorlike fermions, considering some benchmark points in the allowed parameter space., Comment: 22 pages

We construct a scotogenic neutrino mass model introducing large $SU(2)_L$ multiplet fields without adding an extra symmetry. We have introduced extra scalar fields such as a septet, quintet and quartet where we make the vacuum expectation value of quartet scalar to be zero while septet and quintet develop non-zero ones. Then the neutrino mass is generated at one-loop level by introducing quintet fermion. We analyze the neutrino mass matrix taking constraints from lepton flavor violation into account and discuss collider physics regarding charged fermions from large multiplet fields. We have analysed the production and the decays of the quintet fermions, as well as the discovery reach at 14 TeV and 27 TeV LHC., Comment: 21 pages, 6 figures, minor corrections are made

Extant anomalies in several semileptonic $B$-meson decays argue for physics beyond the Standard Model. Measurements of both neutral-current decays (such as $R_K$, $R_{K^*}$ and $B_s\rightarrow \phi\mu\mu$) as well as charged-current ones- $R(D)$ and $R(D^*)$ -provide strong hints for the violation of lepton flavor universality. Recent studies have shown that a class of effective field theory (EFT) models may explain such anomalies in terms of only a few parameters which can be determined phenomenologically. In this literature, we examine such resolutions in the context of the requisite $(\bar{s}$ $b$)($\bar\tau\ \tau)$ operator, and look for its signals at the 13 TeV LHC, with a final state of one $b$-jet, and an oppositely charged $\mu$-$\tau$ pair, with the muon coming from the decay of one of the $\tau$ leptons. We obtain discovery and exclusion limits on the model parameters as a function of luminosity at the 13 TeV LHC., Comment: 19 pages, 19 figures, References added, Figures are changed

We study the effects of including Yukawa-like dimension-5 operators in the Georgi-Machacek model where the Standard Model is augmented with triplet scalars. We focus only on the charged Higgs sector and investigate the constraints arising from radiative B-meson decays, neutral B-meson mixing and precision measurement of Zbb vertex. We observe that the inclusion of the dimension-5 operators causes substantial alteration of the limits on the charged Higgs masses and the vacuum expectation value of the triplets, derived otherwise using only the dimension-4 operators., Comment: 11 pages, 2 captioned figures, minor changes in text, to appear in Phys. Rev. D

We study in detail the collider signatures of an $SU(2)_R$ fermionic quintuplet in the framework of left-right symmetric model in the context of the 13 TeV LHC. Apart from giving a viable dark matter candidate ($\chi^0$), this model provides unique collider imprints in the form of same-sign multileptons through the decays of multi-charged components of the quintuplet. In particular, we consider the scenario where the quintuplet carries $(B - L) = 4$ charge, allowing for the presence of high charge-multiplicity particles with relatively larger mass differences among them compared to $(B - L)$ = 0 or 2. In this paper, we mainly focus on the same-sign n-lepton signatures (nSSL). We show that with an integrated luminosity of 500 $fb^{-1}$, the mass of the neutral component, $M_{\chi^0} \leq 480~(800)$ GeV can be excluded at 95\% CL in the 2SSL (3SSL) channel after imposing several selection criteria. We also show that a $5\sigma$ discovery is also achievable if $M_{\chi^0} \leq 390~(750)$ GeV in the 2SSL (3SSL) channel with 1000 $fb^{-1}$ integrated luminosity., Comment: 24 pages, 7 tables, 12 figures. Comments are welcome. Some modifications in the text for better understanding. Few references added. Accepted in JHEP

We systematically study the modifications in the couplings of the Higgs boson, when identified as a pseudo Nambu-Goldstone boson of a strong sector, in the light of LHC Run 1 and Run 2 data. For the minimal coset SO(5)/SO(4) of the strong sector, we focus on scenarios where the standard model left- and right-handed fermions (specifically, the top and bottom quarks) are either in 5 or in the symmetric 14 representation of SO(5). Going beyond the minimal 5L-5R representation, to what we call here the 'extended' models, we observe that it is possible to construct more than one invariant in the Yukawa sector. In such models, the Yukawa couplings of the 125 GeV Higgs boson undergo nontrivial modifications. The pattern of such modifications can be encoded in a generic phenomenological Lagrangian which applies to a wide class of such models. We show that the presence of more than one Yukawa invariant allows the gauge and Yukawa coupling modifiers to be decorrelated in the 'extended' models, and this decorrelation leads to a relaxation of the bound on the compositeness scale (f > 640 GeV at 95% CL, as compared to f > 1 TeV for the minimal 5L-5R representation model). We also study the Yukawa coupling modifications in the context of the next-to-minimal strong sector coset SO(6)/SO(5) for fermion-embedding up to representations of dimension 20. While quantifying our observations, we have performed a detailed chi-square fit using the ATLAS and CMS combined Run 1 and available Run 2 data., Comment: 23 pages, 6 captioned figures, 6 tables, footnote added, references updated, matches version published in JHEP

We discuss the resummation of the Goldstone boson contributions to the effective potential of the Minimal Supersymmetric Standard Model (MSSM). This eliminates the formal problems of spurious imaginary parts and logarithmic singularities in the minimization conditions when the tree-level Goldstone boson squared masses are negative or approach zero. The numerical impact of the resummation is shown to be almost always very small. We also show how to write the two-loop minimization conditions so that Goldstone boson squared masses do not appear at all, and so that they can be solved without iteration., Comment: 28 pages. v2: references added

We study the prospects for excluding or discovering vectorlike leptons using multilepton events at the LHC. We consider models in which the vectorlike leptons decay to tau leptons. If the vectorlike leptons are weak isosinglets, then discovery in multilepton states is found to be extremely challenging. For the case that the vectorlike leptons are weak isodoublet, we argue that there may be an opportunity for exclusion for masses up to about 275 GeV by direct searches with existing LHC data at sqrt{s}=8 TeV. We also discuss prospects for exclusion or discovery at the LHC with future sqrt{s}=13 TeV data., Comment: 36 pages. v2: references added

We study the prospects for LHC discovery of a narrow resonance that decays to two Higgs bosons, using the final state of two photons and two bottom jets. Our work is motivated in part by a scenario in which two-body flavor-preserving decays of the top squark are kinematically forbidden. Stoponium, a hadronic bound state of the top squark and its anti-particle, will then form, and may have a large branching fraction into the two Higgs boson final state. We estimate the cross-section needed for a 5-sigma discovery at the 14 TeV LHC for such a narrow di-Higgs resonance, using the invariant mass distributions of the final state bottom jets and photons, as a function of the integrated luminosity. The results are also applicable to any other di-Higgs resonance produced by gluon fusion., Comment: 15 pages v3:Modified cuts on photon pT's and fake photon backgrounds added