The mixing between third and second (or first) generation squarks is very small in supersymmetric models with minimal flavor violation such as gauge-, anomaly- or gaugino-mediation. An opportunity to measure this mixing will arise if the lightest stop is close enough in mass to the lightest neutralino, so that the decays into third generation quarks are kinematically forbidden. We analyze under which circumstances it might become possible to measure at the Large Hadron Collider (LHC) the rate of the flavor changing stop decays.
Models of minimal lepton flavor violation where the seesaw scale is higher than the relevant flavor scale predict that all lepton flavor violation is proportional to the charged lepton Yukawa matrix. If extra vector-like leptons are within the reach of the LHC, it will be possible to test the resulting predictions in ATLAS/CMS.
We show that in supersymmetric models with explicit flavor lepton number violation due to soft supersymmetry breaking mass terms there could be detectable flavor lepton number violation in slepton decays. We estimate LHC discovery potential of the lepton flavor number violation in slepton decays.
A new process with the lepton flavor violation (LFV) is presented in the setup for LHC. The LFV is induced by the one-loop effect through Higgs bosons in the framework of the type-III two Higgs doublet model. It is demonstrated that the vast of parameter space in the Yukawa sector could be accessed by current and future LHC experiments.
Recent results from Super Kamiokande suggest $ν_μ-ν_τ$ mixing and hence lepton flavor violation. In supersymmetric models, this flavor violation may have implications for the pattern of slepton masses and mixings. Possible signals for this mixing in the decays of sleptons produced at the LHC are discussed. The sensitivity expected is compared to that of rare decays such as $τ\to μγ$.
The physics underlying quark and lepton masses and mixings (the "flavor problem") is the least well understood aspect of the Standard Model. Some questions of flavor physics, and ways in which the LHC can help shed light on this problem, are described.
We consider the possibility that dark matter can communicate with the Standard Model fields via flavor interactions. We take the dark matter to belong to a "dark sector" which contains at least two types, or "flavors", of particles and then hypothesize that the Standard Model fields and dark matter share a common interaction which depends on flavor. As, generically, interaction eigenstates and mass eigenstates need not coincide, we consider both flavor-changing and flavor-conserving interactions. These interactions are then constrained by meson decays, kaon mixing, and current collider bounds,…
In a generic supersymmetric extension of the Standard Model, there will be lepton flavor violation at a neutral gaugino vertex due to misalignment between the lepton Yukawa couplings and the slepton soft masses. Sleptons produced at the LHC through the cascade decays of squarks and gluinos can give a sizable number of events with 4 leptons. This channel could give a clean signature of supersymmetric lepton flavor violation under conditions which are identified.
In supersymmetric scenarios, the seesaw mechanism involving heavy right-handed neutrinos implies sizable lepton flavor violation (LFV) in the slepton sector. We discuss the potential of detecting LFV processes at the LHC in mSUGRA+seesaw scenarios and for general mixing in either the left- or right-handed slepton sector. The results are compared with the sensitivity of rare LFV mu -> e gamma decay experiments.
We examine the flavor dependence of the nuclear modification factor $R_{AA}$ in the pQCD calculations at LHC energies. The computations are performed accounting for radiative and collisional parton energy loss with running coupling constant. Our results show that the recent LHC data on the $R_{AA}$ for charged hadrons, D-mesons and non-photonic electrons agree reasonably with the pQCD picture of the parton energy loss with the dominating contribution from the radiative mechanism.
Models with a non-universal Z' exhibit in general flavor changing neutral currents (FCNC) at tree-level. When the Z' couplings favor the third generation, flavor changing transitions of the form Z'tc and Z'tu could be large enough to be observable at the LHC. In this paper we explore this possibility using the associated production of a single top-quark with the Z' and find that integrated luminosities of a few hundred fb$^{-1}$ are necessary to probe the interesting region of parameter space.
We study the effects of a set of dimension six flavor changing effective operators on several processes of production of top quarks at the LHC. Namely, top anti-top production and associated production of a top and a gauge or Higgs boson. Analytical expressions for the cross sections of these processes are derived and presented.
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.
Associated production of different flavor heavy quarks can provide a probe for $W'$ bosons at the LHC. We study $pp\to t'\bar{b'}X$ process with the subsequent decays $t'\to W^+b$ and $\bar{b'}\to W^-W^+\bar b$, and compare the results with the $t\bar{b}$ final state. The effects of the $W'$ boson to the different flavor pair production cross section are shown to be important in some parameter region for the heavy quark masses of 600 and 700 GeV. We present accessible mass limits for the $W'$ boson at the LHC with $\sqrt s$=14 TeV.
I discuss a model of lepton flavor symmetry based on the non-Abelian finite group T(7) and the gauging of B-L, which has a residual Z(3) symmetry in the charged-lepton Yukawa sector, allowing it to be observable at the Large Hadron Collider (LHC) from the decay of the new Z' gauge boson of this model to a pair of scalar bosons which the unusual highly distinguishable final states tau(-)tau(-)mu(+)e(+).
The suppression of flavor and CP violation in supersymmetric theories may be due to the mechanism responsible for the structure of the Yukawa couplings. We study model independently the compatibility between low energy flavor and CP constraints and observability of superparticles at the LHC, assuming a generic correlation between the Yukawa couplings and the supersymmetry breaking parameters. We find that the superpotential operators that generate scalar trilinear interactions are generically problematic. We discuss several ways in which this tension is naturally avoided. In particular, we foc…
We study extensions of the standard model with additional colored scalar fields which can couple directly to quarks. Natural suppression of flavor changing neutral currents implies minimal flavor violation, and fixes the scalars to transform as (8,2)_1/2 under the SU(3) X SU(2) X U(1) gauge symmetry. We explore the phenomenology of the standard model with one additional (8,2)_1/2 scalar, and discuss how this extension can modify flavor physics and the Higgs boson production rate at the LHC. Custodial SU(2) symmetry can be implemented for the octet scalars since they transform as a real color r…
Flavor physics has been crucial in the development of particle physics and it will keep being so in the future. Nowadays, this kind of processes, in particular lepton flavor changing observed in neutrino oscillations, give us the clearest evidence of the fact that the Standard Model of fundamental interactions needs to be modified. Some of the most popular theories that try to asses this issue postulate the existence of new heavy right-handed neutrinos, with masses in the energy range that the LHC experiment is currently exploring. In this thesis, we study the connection between the possible e…
Some of the open questions on jet quenching are expected to be clarified by measuring heavy-flavored mesons at high transverse momentum. The formalism based on radiative in-medium energy-loss, which describes other high-pt results at RHIC, gives definite predictions for the suppression of charm and beauty quarks. However, the uncertainties from both contributions to the observed electrons make the interpretation of the data difficult due to the absence of a well calibrated benchmark. We review the present situation as well as the consequences for the future LHC. We also comment on the use of h…
We compute and analyze the Flavor-Changing Neutral Current (FCNC) interactions of Minimal Supersymmetric Standard Model Higgs bosons (h = h0, H0, A0) with heavy quarks (top and bottom), focusing on the strongly-interacting sector. We correlate the Higgs bosons production cross-section at the LHC with the FCNC decay branching ratios and find the maximum allowed values of the production rates, sigma(pp -> h -> qq') = sigma(pp -> h) x B(h -> qq') (qq'= tc or bs) after taking into account limits from low energy data on flavor-changing interactions. We single out the top channel, with a maximum pro…
Baryon triality (B3) is a Z3 discrete symmetry that can protect the proton from decay. Although its realization does not require supersymmetry, it is particularly appealing in the supersymmetry as an alternative to the popular R-parity. We discuss the issues in gauging B3, and present the minimal supersymmetric model with B3 as the remnant discrete symmetry of a TeV scale U(1) gauge symmetry. A flavor-dependent U(1) charge is necessary to achieve this, and it results in very distinguishable and flavorful predictions for the LHC experiments. We find a complementarity between a 2-lepton sneutrin…
We study the modeling of $t$-channel single top-quark production at Large Hadron Collider (LHC) energies. We compare predictions at next-to-next-to-leading order in a 5-flavor scheme to those of next-to-leading order in a 4-flavor scheme, finding the two schemes agree within a few percent in general for the shape of kinematic distributions of the top quark. The predictions in the 5-flavor scheme show strong stability for both normalization and distributions, and are superior to those of the 4-flavor scheme at comparable orders. We present comparisons of the predictions with LHC data. Our findi…
The LHC will have unprecedented sensitivity to flavor-changing neutral current (FCNC) top quark decays, whose observation would be a clear sign of physics beyond the standard model. Although many details of top flavor violation are model dependent, the standard model gauge symmetries relate top FCNCs to other processes, which are strongly constrained by existing data. We study these constraints in a model independent way, using a low energy effective theory from which the new physics is integrated out. We consider the most important operators which contribute to top FCNCs and analyze the curre…
Observation of some low-energy processes in the flavor physics regime may require the existence of supersymmetry with two relatively large R-parity-violating couplings of the LQD-type, together with reasonably light superparticles. At the LHC, such interactions would be expected to give rise to clear signals with convenient leptonic triggers, including some multileptons of the same sign. We undertake a detailed investigation of these signals taking care to correlate with low-energy requirements and taking proper account of the Standard Model backgrounds as well as the R-parity-conserving secto…
We study an MSSM model with bilinear R-parity violation which is capable of explaining neutrino data while leading to testable predictions for ratios of LSP decay rates. Further, we estimate the precision with which such a measurement could be carried out at the LHC.
We study the fermionic couplings of the neutral Higgs bosons in the THDM, assuming a four-texture structure for the Yukawa matrices. We then derive the low-energy constraints on the model, focusing in b-quark and lepton physics, and apply them to study Higgs boson detection at future colliders.
For a new family-nonuniversal gauge interaction to be accessible at the LHC it will most likely couple preferentially to the third family. By coupling to all members of the third family the production of a new gauge boson (the $X$ with $M_X\approx1$ TeV) will lead to final states with a distinctive $τ^+τ^-$ pair. We study the mass reconstruction of the $X$ and the cuts that can enhance signal to background. The $X$ boson should be associated with the physics of flavor and in the simplest picture a fourth family. We discuss how the mass mixing between the third and fourth families affects the $…
Charged Lepton Flavor Violation (cLFV) processes like $ μ\rightarrow e γ$ are rare decay processes, that are another signature of physics beyond Standard Model (BSM). These processes have been studied in various models, that could explain neutrino oscillations and mixings. In this work, we present bounds on cLFV decay $ μ\rightarrow e γ$ in a $ μ$-$ τ$ symmetric SUSY SO(10) theory, using type I seesaw mechanism. The updated constraints on BR($ μ\rightarrow e γ$) from MEG experiment, recently measured value of Higgs mass at LHC and value of $θ_{13}$ from reactor data have been used. We present …
Motivated by the null results of LHC searches, which together with the Higgs mass, severely constrain minimal supersymmetric extensions of the standard model, we adopt a model-independent approach to study charged slepton flavor. We examine a number of simplified models, with different subsets of sleptons, electroweak gauginos, and Higgsinos, and derive the allowed slepton flavor dependence in the region probed by current LHC searches, and in the region relevant for the 14 TeV LHC. We then study the impact of the allowed flavor dependence on lepton plus missing energy searches. In some cases, …
Within the context of vector mediators, is a new signal observed in flavor changing interactions, particularly in the neutral mesons systems $K^{0}-\bar{K}^{0}$, $D^{0}-\bar{D}^{0}$ and $B^0-\bar{B^0}$, consistent with dilepton resonance searches at the LHC? In the attempt to address this very simple question, we discuss the complementarity between flavor changing neutral current (FCNC) and dilepton resonance searches at the LHC run 2 at $13$TeV with $3.2\, {\rm fb^{-1}}$ of integrated luminosity, in the context of vector mediators at tree level. Vector mediators, are often studied in the flav…
A simple covariant formalism to describe flavor and CP violation in the left-handed quark sector in a model independent way is provided. The introduction of a covariant basis, which makes the standard model approximate symmetry structure manifest, leads to a physical and transparent picture of flavor conversion processes. Our method is particularly useful to derive robust bounds on models with arbitrary mechanisms of alignment. Known constraints on flavor violation in the K and D systems are reproduced in a straightforward manner. Assumptions-free limits, based on top flavor violation at the L…
We revisit the exclusive signature $e^\pm (μ^\pm) + b\bar b$ in the associated production of the intermediate mass Higgs boson with a $W$ boson. We show that it is feasible to use this signature to identify the Higgs boson in the lower intermediate mass region ($90$ to $130$ GeV) at the LHC with reasonable acceptance cuts by assuming effective bottom-jet identification. We further demonstrate that the background can be reduced with judicious cuts down to the level of the signal.
A simple formalism to describe flavor and CP violation in a model independent way is provided. Our method is particularly useful to derive robust bounds on models with arbitrary mechanisms of alignment. Known constraints on flavor violation in the K and D systems are reproduced in a straightforward and covariant manner. Assumptions-free limits, based on top flavor violation at the LHC, are then obtained. In the absence of signal, with 100 fb^{-1} of data, the LHC will exclude weakly coupled (strongly coupled) new physics up to a scale of 0.6 TeV (7.6 TeV), while at present no general constrain…
Results are presented of a feasibility study of techniques for measuring the mass of the lightest chargino at the CERN LHC. These results suggest that for one particular mSUGRA model a statistically significant chargino signal can be identified and the chargino mass reconstructed with a precision of order 11% for of order 100 fb-1 of data.
In Split-Supersymmetry models, where the only non-Standard Model states produceable at LHC-energies consist of a gluino plus neutralinos and charginos, it is conventionally accepted that only mass differences among these latter are measureable at the LHC. The present work shows that application of a simple `Kinematic Selection' technique allows full reconstruction of neutralino and chargino masses from one event, in principle. A Monte Carlo simulation demonstrates the feasibilty of using this technique at the LHC.
Following recent ATLAS and CMS publications we interpret the results of their Higgs searches in terms of Standard Model operators. For a Higgs mass of 125 GeV we determine several Higgs couplings from 2011 data and extrapolate the results towards different scenarios of LHC running. Even though our analysis is limited by low statistics we already derive meaningful constraints on modified Higgs sectors.
The LHC offers a unique opportunity to investigate an ample spectra of phenomenous ranging from the Electro-Weak (EW) to the QCD sector of the Standard Model (SM). Among the quantities which can be measured in the LHC experiments are the CP and production asymmetries for several particles in a wide variety of decay modes. In this work we discuss about the interplay between production and CP asymmetries for particles produced in proton-proton interactions and the effects of one on the measurement of the other. This kind of effects are not present in flavor symmetric machines like the Tevatron o…
We show that simultaneous precision measurement of the CP-violating phase in time-dependent Bs --> J/psi phi study and the Bs --> mu+ mu- rate, together with measuring m_t' by direct search at the LHC, would determine V_{t's}^*V_{t'b} and therefore the b --> s quadrangle in the four-generation standard model. The forward-backward asymmetry in B --> K* l+ l- provides further discrimination.
Motivated by the rencent LHC data on the lepton-flavor violating (LFV) decays $h\to \ell_1 \ell_2$ and $B_{s,d}\to \ell_1 \ell_2$, we study the Higgs-mediated flavor-changing neutral current (FCNC) interactions in the effective field theory (EFT) approach without and with the minimal flavor violation (MFV) hypothesis, and concentrate on the later. After considering the $B$ and $K$ physics data, the various LFV processes, and the LHC Higgs data, severe constraints on the Higgs FCNC couplings are derived, which are dominated by the LHC Higgs data, the $B_s - \bar B_s$ mixing, and the $μ\to e γ$ …
We show in the framework of Higgs triplet model that the lower bound of the neutrino mass is obtained if we can measure $\frac{Γ(Δ^{--}\to ee)}{Γ(Δ^{--}\to μμ)}$ at the LHC.
We consider new physics explanations of the anomaly in the top quark forward-backward asymmetry measured at the Tevatron, in the context of flavor conserving models. The recently measured LHC dijet distributions strongly constrain many otherwise viable models. A new scalar particle in the antitriplet representation of flavor and color can fit the t tbar asymmetry and cross section data at the Tevatron and avoid both low- and high-energy bounds from flavor physics and the LHC. An s-channel resonance in uc to uc scattering at the LHC is predicted to be not far from the current sensitivity. This …
In this paper, we consider a solution to explain the three discrepancies with the standard model (SM) predictions in flavor observables, i.e. anomalies in $B\rightarrow K^\astμ^+μ^-$ and $R_K=\mathcal{B}(B\rightarrow Kμ^+μ^-)/\mathcal{B}(B\rightarrow K e^+e^-)$ at the LHCb and an excess in $h\rightarrow μτ$ at the CMS in the context of R-parity violating (RPV) supersymmetry. We demonstrate that these anomalies can be explained within a unified framework: the minimal supersymmetry model (MSSM) extended with $5+\overline{5}$ vectorlike (VL) particles. The new trilinear RPV couplings involving VL…
There are lots of new physics models which predict an extra neutral gauge boson, referred as Z'-boson. In a certain class of these new physics models, the Z'-boson has flavor-dependent couplings with the fermions in the Standard Model (SM). Based on a simple model in which couplings of the SM fermions in the third generation with the Z'-boson are different from those of the corresponding fermions in the first two generations, we study the signatures of Z'-boson at the Large Hadron Collider (LHC) and the International Linear Collider (ILC). We show that at the LHC, the Z'-boson with mass around…
Probing Flavor-Violating Higgs Decays in the Type-III Two-Higgs-Doublet Model at the LHC and HL-LHC
Instituto de Física, Benemérita Universidad Autónoma de Puebla（普埃布拉自治大学物理研究所）；Centro Interdisciplinario de Investigación y Enseñanza de la Ciencia (CIIEC), Benemérita Universidad Autónoma de Puebla（普埃布拉自治大学交叉科学研究与教育中心）
We show that the discovery channel for dark matter (DM) production at colliders can be through flavor violating interactions resulting in a novel signature of a single top and large missing transverse energy. We discuss several examples where the production of DM is dominated by flavor violating couplings: minimal flavor violating models with a large bottom Yukawa, models with horizontal symmetries, and DM in nontrivial flavor group representations. Discovery at the 7 TeV LHC with a few fb^-1 may already be possible.
A general two Higgs doublet model (2HDM) is adopted to study the signature of flavor changing neutral Higgs (FCNH) decay $ϕ^0 \to t\bar{c}+\bar{t}c$, where $ϕ^0$ could be a CP-even scalar ($H^0$) or a CP-odd pseudoscalar ($A^0$). Measurement of the light 125 GeV neutral Higgs boson ($h^0$) couplings at the Large Hadron Collider (LHC) favor the decoupling limit or the alignment limit of a 2HDM, in which gauge boson and diagonal fermion couplings of $h^0$ approach Standard Model values. In such limit, FCNH couplings of $h^0$ are naturally suppressed by a small mixing parameter $\cos(β-α)$, while…
We investigate the possibility to measure the top quark mass using the collider variable $m_{T2}$ at the LHC experiment. Monte Carlo studies of $m_{T2}$ are performed with the events corresponding to the dilepton decays of $t\bar{t}$ produced at the LHC with 10 $fb^{-1}$ integrated luminosity. Our analysis suggests that the top quark mass can be determined by the $m_{T2}$ variable alone with a good precision at the level of 1 GeV.
Single top quark production is a powerful process to search for new physics signs. In this work we propose and investigate a search for top quark flavor changing neutral currents (FCNC) via a photon using direct single top quark production events in proton-proton collisions at the LHC at CERN. We show that the direct single top quark final state can provide constraints on the strengths of tq$γ$ (top-quark-$γ$) and tqg (top-quark-gluon) FCNC couplings simultaneously. Results of a search for direct single top quark production at the LHC at a center-of-mass energy of 8 TeV performed by the ATLAS …
The CP violation of the neutral $B$ meson is the important phenomenon to search for the new physics. The like-sign dimuon charge asymmetry observed by the D$Ø$ Collaboration indicates the CP-violating new physics in the $B_s-\bar B_s$ mixing. On the other hand, LHCb observed the CP-violating asymmetry in $B_s^0\to J/ψϕ$ and $B_s^0\to J/ψf_0(980)$, which is consistent with the SM prediction. However, there is still room for new physics of the CP violation. The CKMfitter has presented the allowed region of the new physics parameters taking account of the LHCb data. Based on these results, we dis…
We explored the possibility that Higgs coupling to new physics violates flavor universality. In particular, we parameterize such models with dimension-six effective operators which modify the coupling between the first generation quarks, Higgs boson, and $Z$ boson. Through the use of boosted Higgsstrahlung events at both the HL-LHC and potential future hadron colliders, as well as existing ATLAS data for background estimates, we projected constraints on the scale of new physics as a function of the Wilson coefficient. The high energy $Zh$ process will provide unique information about these cla…
We consider the ratio between the double and single Higgs production cross sections and examine the prospect of measuring the trilinear Higgs self-coupling using this observable. Such a ratio has a reduced theoretical (scale) uncertainty than the double Higgs cross section. We find that with 600/fb, the 14 TeV LHC can constraint the trilinear Higgs self coupling to be positive, and with 3000/fb one could measure it with a +30 % {-20 %}) accuracy.
We consider the top forward-backward (FB) asymmetry at the Tevatron and top charge asymmetry at the LHC within chiral U(1)^\prime models with flavor-dependent U(1)^\prime charges and flavored Higgs fields, which were introduced in the ref. [65]. The models could enhance not only the top forward-backward asymmetry at Tevatron, but also the top charge asymmetry at LHC, without too large same-sign top pair production rates. We identify parameter spaces for the U(1)^\prime gauge boson and (pseudo)scalar Higgs bosons where all the experimental data could be accommodated, including the case with abo…
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 $B_s\rightarrow ϕμμ$) 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 $(\bar{s}$ $b$…
In this paper we revisit the idea of measuring the magnetic dipole moments of the charm baryons and, in particular, of charmed Lambda by studying the spin precession induced by the strong effective magnetic field inside the channels of a bent crystal. We present a detailed sensitivity study showing the feasibility of such an experiment at the LHC in the coming years.
