New Physics searches at the LHC have increased significantly lower bounds on unknown particle masses. This increases quite dramatically the tension in the interpretation of the data: low energy precision data which are predicted accurately by the SM (LEP observables like M_W or loop induced rare processes like B --> X_s gamma or B_s --> mu+mu-) and quantities exhibiting an observed discrepancy between SM theory and experiment, most significantly found for the muon g-2, seem to be in conflict now. (g-2)_mu appears to be the most precisely understood observable which at the same time reveals a 3-4 sigma deviation between theory and experiment and thus requires a significant new physics contribution. The hints for a Higgs of mass about 125 GeV, which is precisely what SUSY extensions of the SM predict, seem to provide a strong indication for SUSY. At the same time it brings into serious trouble the interpretation of the (g-2)_mu deviation as a SUSY contribution.
I report here on the systematic analysis at Tevatron of the R-parity violating SUSY signals which correspond to the possible solution of anomalous HERA events.
We derive constraints on the mass insertion parameters from the recent measurements of B_s - B_s bar mixing, and discuss their implications on SUSY breaking mediation mechanisms and SUSY flavor models. Some SUSY flavor models are already excluded or disfavored by B_s - B_s bar mixing. We also discuss how to test the SM and SUSY models in the future experiments, by studying other CP violating observables related to b -> s transition, such as the time-dependent CP asymmetry in B -> phi K_S and the direct CP asymmetry in B -> X_s gamma.
I discuss some essential features of the electroweak hierarchy problem and the ensuing motivation for weak-scale supersymmetry. Taking the hierarchy problem seriously, null results in searches for SUSY at the LHC favor specific regions of SUSY parameter space. More broadly, they suggest investigating a variety of alternative approaches to the hierarchy problem with diverse experimental signatures.
The implications of the LHC SUSY searches as well as the discovery of a new bosonic state compatible with the lightest Higgs boson will be discussed in the context of constrained and general MSSM scenarios. Exploring the MSSM through the Higgs sector is an alternative and complementary path to direct searches, and tight constraints on the MSSM parameter space can be obtained.
We consider a plausible scenario in the Minimal Supersymmetric Standard Model (MSSM) where all the genuine supersymmetric (SUSY) particles are heavier than the electroweak scale. In this situation, indirect searches via their radiative corrections to low energy observables are complementary to direct searches, and they can be crucial if the SUSY masses are at the TeV energy range. We summarize the most relevant heavy SUSY radiative effects in Higgs boson physics and emphasize those that manifest a non-decoupling behaviour. We focus, in particular, on the SUSY-QCD non-decoupling effects in ferm…
Thermal leptogenesis is an attractive mechanism for generating the baryon asymmetry of the Universe. However, in supersymmetric models, the parameter space is severely restricted by the gravitino bound on the reheat temperature $T_{RH}$. Using a parametrisation of the seesaw in terms of weak-scale inputs, the low-energy footprints of thermal leptogenesis are discussed.
Higgs Mass and CP violating Phases Implications on the SUSY Breaking Scale in MSSM
Center of Fundamental Physics CFP, Zewail City of Science and Technology（扎威尔科学与技术城基础物理中心）；Department of Physics, Faculty of Science, University of Alexandria（亚历山大大学理学院物理系）
We study the effects of scalar-pseudoscalar mixing induced from quantum loop on $ε'/ε$ in SUSY models with $\tanβ\sim m_{t}/m_{b}$. We find that even the non-universal soft ${\cal A}^{d}$ term and Yukawa matrix, $Y^{d}$, are hermitian, the predicted value of $|ε'/ε|$ can be consistent with the measured results of NA48 and KTeV. And also the EDMs are compatible with experimental bounds.
This talk presents the detection issues for the lightest slepton \tildeτ_1 at a future e+e- TeV collider given the dark matter constraints set on the SUSY mass spectrum by the WMAP results. Two methods for measuring its mass m_{\tildeτ_1} and the resulting precision on the dark matter density are briefly discussed in the SUSY mSUGRA scenario with R-parity conservation when the mass difference between m_{\tildeτ_1} and that of the lightest neutralino is small (a few GeV). The analysis is performed with TESLA parameters in both head-on and crossing angle modes.
This is an addendum to the previous publication, P. Ko and J.-h. Park, Phys. Rev. D80, 035019 (2009). The semileptonic charge asymmetry in B_s decays is discussed in the context of general MSSM with gluino-mediated flavor and CP violation in light of the recent measurements at the Tevatron.
We correct our treatment of decays of the lightest chargino to final states containing the lightest neutralino in the case where the chargino and neutralino masses differ by less than 1 GeV. A brief summary of the phenomenological implications is given.
We revisit the standard argument to estimate the scale of new physics (NP) beyond the SM, based on the sensitivity of the Higgs mass to quadratic divergences. Although this argument is arguably naive, the corresponding estimate, Lambda_SM < 2-3 TeV, works reasonably well in most cases and should be considered a conservative bound, as it ignores other contributions to the Higgs mass which are potentially large. Besides, the possibility of an accidental Veltman-like cancellation does not raise significantly Lambda_SM. One can obtain more precise implications from fine-tuning arguments in specifi…
The favoured R-parity violating SUSY scenarios for the anomalous HERA events correspond to top and charm squark production via the $λ'_{131}$ and $λ'_{121}$ couplings. In both cases the corresponding electronic branching fractions of the squarks are expected to be $\ll 1$. Consequently the canonical leptoquark signature is incapable of probing these scenarios at the Tevatron collider over most of the MSSM parameter space. We suggest alternative signatures for probing them at Tevatron, which seem to be viable over the entire range of MSSM parameters.
This paper presents the detection issues for the lightest slepton \tildeτ_1 at a future e^+e^- TeV collider given the dark matter constraints set on the SUSY mass spectrum by the WMAP results. It intends to illustrate the importance of an optimal detection of energetic electrons in the very forward region for an efficient rejection of the γγbackground. The TESLA parameters have been used in the case of head-on collisions and in the case of a 10, mrad half crossing angle.
In minimal SUSY-GUT models with $M_{SUSY}\ltap 1$ TeV, the renormalization group equations have a solution dominated by the infrared fixed point of the top Yukawa coupling. This fixed point predicts $m_t=(200\; {\rm GeV})\sin β$; combined with the LEP results it excludes $m_t\ltap 130$ GeV. For $m_t$ in the range 130-160 GeV, we discuss the sensitivity of the $m_t$ fixed point result to GUT threshold corrections and point out the implications for Higgs boson searches. The lightest scalar $h$ has mass 60-85 GeV and will be detectable at LEPII. At SSC/LHC, each of the five scalars $h$, $H$, $A$,…
Both ATLAS and CMS have published results of SUSY searches putting limits on SUSY parameters and masses. A non-discovery of SUSY in the next two years would push these limits further. On the other hand, precision data of low energy measurements and the dark matter relic density favor a light scale of supersymmetry. Therefore we investigate if supersymmetry -- more specifically the highly constraint model mSUGRA -- does at all agree with precision data and LHC exclusions at the same time, and whether the first two years of LHC will be capable of excluding models of supersymmetry. We consider th…
In minimal SUSY-GUT models with $M_{SUSY}\alt 1$ TeV, the renormalization group equations have a solution dominated by the infrared fixed point of the top Yukawa coupling. This fixed point predicts $m_t\simeq (200\; {\rm GeV})\sin β$; combined with the LEP results it excludes $m_t\alt 130$ GeV. For $m_t$ in the range 130--160 GeV, it predicts that the lightest scalar $h$ has mass 60--85 GeV (detectable at LEP\,II). At SSC/LHC, each of the five scalars $h$, $H$, $A$, $H^{\pm }$ may be detectable, but not all of them together; in one parameter region none would be detectable.
We investigate the probability to find a b or tau in SUSY production with the mSUGRA model. We find that in the entire parameter space the probability per event to find a b-jet of E_T^b > 50 GeV within CMS acceptance (eta < 2.4) is significant for all tan(beta), varying from a 10 % level to 90 % depending on the m_0, m_1/2 region. The probabilities per event to find a tau with the same kinematical cuts is also significant and it increases sharply with tan(beta). These findings point to the central role a microvertex device would play in case that SUSY (mSUGRA) is indeed realized in nature and …
We consider $B_s \to μ^+ μ^-$ and the muon $(g-2)_μ$ in various SUSY breaking mediation mechanisms. If the decay $B_s \to μ^+ μ^-$ is observed at Tevatron Run II with a branching ratio larger than $\sim 2 \times 10^{-8} $, the noscale supergravity (including the gaugino mediation), the gauge mediation scenario with small number of messenger fields and low messenger scale, and a class of anomaly mediation scenarios will be excluded, even if they can accommodate a large muon $(g-2)_μ$. On the other hand, the minimal supergravity scenario and similar mechanisms derived from string models can acco…
Recently, the ATLAS and CMS collaborations have announced exciting hints for a Standard Model-like Higgs boson at a mass of approximately 125 GeV. In this paper, we explore the potential consequences for the MSSM and low scale SUSY-breaking. As is well-known, a 125 GeV Higgs implies either extremely heavy stops (>~ 10 TeV), or near-maximal stop mixing. We review and quantify these statements, and investigate the implications for models of low-scale SUSY breaking such as gauge mediation where the A-terms are small at the messenger scale. For such models, we find that either a gaugino must be su…
Recently BABAR and Belle have measured anomalous large transverse polarizations in some pure penguin $B \to VV$ decays, which might be inconsistent with the Standard Model expectations. We try to explore its implications for R-parity violating (RPV) supersymmetry. The QCD factorization approach is employed for the hadronic dynamics of B decays. We find that it is possible to have parameter spaces solving the anomaly. Furthermore, we have derived stringent bounds on relevant RPV couplings from the experimental data, which is useful for further studies of RPV phenomena.
We discuss the characteristic low energy phenomenological implications of an SU(5) Supersymmetric Grand Unified Theory (SUSY GUT) whose flavour structure is controlled by the family symmetry S4 x U(1), which provides a good description of all quark and lepton masses, mixings as well as CP violation. Although the model closely mimics Minimal Flavour Violation (MFV) as shown in arXiv:1511.07886, here we focus on the differences. We first present numerical estimates of the low energy mass insertion parameters, including canonical normalisation and renormalisation group running, for well-defined r…
We outline several well-motivated models in which GUT boundary conditions for SUSY breaking are non-universal. The diverse phenomenological implications of the non-universality for SUSY discovery at LEP2, the Tevatron, the LHC and the NLC are sketched.
Global frequentist fits to the CMSSM and NUHM1 using the MasterCode framework are updated to include the public results of searches for supersymmetric signals using \sim 1/fb of LHC data recorded by ATLAS and CMS and \sim 0.3/fb of data recorded by LHCb. We also include the constraints imposed by the electroweak precision and B-physics observables, the cosmological dark matter density and the XENON100 search for spin-independent dark matter scattering. Finally we also investigate the impact of a possible Higgs signal around 125 GeV. The various constraints set new bounds on the parameter space…
The phenomenological implications of the E6 inspired supersymmetric models based on the Standard Model gauge group together with extra U(1)_N gauge symmetry under which right-handed neutrinos have zero charge are examined. In these models single discrete symmetry forbids the tree-level flavour changing processes and the most dangerous operators that violate baryon and lepton numbers. The two-loop renormalisation group flow of the gauge and Yukawa couplings is explored and the qualitative pattern of the Higgs spectrum in the case of the quasi-fixed point scenario is discussed. These E6 inspired…
We study the new physics (NP) implications of the recently reported 3.2 sigma Standard Model (SM) deviation in the like-sign dimuon asymmetry at the Tevatron. Assuming that new physics only enters the B(s) mixing amplitude we explore the implications for generic new physics, general supersymmetric (SUSY) models and also SUSY SU(5). In the case of SUSY SU(5) we exploit the GUT scale relationship between slepton and squark soft masses to predict rates for lepton flavour violation (LFV). The predicted rates for tau --> mu + gamma are found to be detectable at future Super-B factories.
For the case of the MSSM and the most general form of the NMSSM (GNMSSM) we determine the reduction in the fine tuning that follows from allowing gaugino masses to be non-degenerate at the unification scale, taking account of the LHC8 bounds on SUSY masses, the Higgs mass bound, gauge coupling unification and the requirement of an acceptable dark matter density. We show that low-fine tuned points fall in the region of gaugino mass ratios predicted by specific unified and string models. For the case of the MSSM the minimum fine tuning is still large, approximately 1:60 allowing for a 3 GeV unce…
The Atlas and CMS collaborations have both reported an excess of events in the WW\star \rightarrow \ell+\ell- + ETmiss search channel, which could be the first evidence for the Higgs boson. In the context of the MSSM, the lightest SUSY Higgs scalar h is expected to occur with mass mh = 135 GeV, depending on the range of SUSY parameters scanned over. Since the h \rightarrow WW\star branching fraction falls swiftly with decreasing mh, a signal in the WW\star channel would favor an h at the high end of its predicted mass range. We scan over general GUT scale SUSY model parameters to find those wh…
One-loop contributions to the Higgs potential at finite temperatures are discussed in the supersymmetric standard model with four Higgs doublet chiral superfields as well as a pair of charged singlet chiral superfields. The mass of the lightest Higgs boson $h$ is determined only by the D-term at the tree-level in this model, while the triple Higgs boson coupling for $hhh$ can receive a significant radiative correction. The same nondecoupling effect can also contribute to realize the sufficient first order electroweak phase transition, which is required for a successful scenario of electroweak …
From several points of view it is strongly suggested that the current universe is unstable and will ultimately decay to one that is exactly supersymmetric (susy). The possibility that atoms and molecules form in this future universe requires that the degenerate electron/selectron mass is non-zero and hence that electroweak symmetry breaking (EWSB) survives the phase transition to exact susy. However, the minimal supersymmetric standard model (MSSM) and several of its extensions have no EWSB in the susy limit. Among the extended higgs models that have been discussed one stands out in this regar…
We study moduli-dominated SUSY breaking within the framework of string models. This type of SUSY breaking in general leads to non-universal soft masses, i.e. soft scalar masses and gaugino masses. Further gauginos are lighter than sfermions. This non-universality has phenomenologically important implications. We investigate radiative electroweak symmetry breaking in the mass spectrum derived from moduli-dominated SUSY breaking, where the lightest chargino and neutralino are almost gauginos. Moreover, constraints from the branching ratio of $b \to s γ$ and the relic abundance of the LSP are als…
We review results from our frequentist analysis of the parameter space of the pMSSM10, in which the following 10 soft SUSY-breaking parameters are specified independently at the mean scalar top mass scale Msusy = \sqrt{M_stop1 M_stop2}: the gaugino masses M_{1,2,3}, the 1st-and 2nd-generation squark masses M_squ1 = M_squ2, the third-generation squark mass M_squ3, a common slepton mass M_slep and a common trilinear mixing parameter A, the Higgs mixing parameter mu, the pseudoscalar Higgs mass M_A and tan beta, the ratio of the two Higgs vacuum expectation values. We implemented the LHC searches…
If SUSY exists at the TeV scale, finding it at the LHC should be quite easy. The more difficult problem is to separate the various SUSY channels and to measure masses and other parameters. Substantial progress on this has been made within the ATLAS and CMS Collaborations.
We show that one of the ways of obtaining consistency between the idea of supersymmetric grand unification and an apparent low value of $α_{strong}(M_Z)\simeq .11$ indicated by several low energy experiments is to have an intermediate scale corresponding to a local $B-L$ symmetry breaking around the mass scale of $10^{10}$ to $10^{12}$ GeV. We discuss the realization of this idea within the framework of supersymmetric $SO(10)$ grand unified theories with spectra of particles derivable from simple superstring-inspired versions of this model. We then study the $b-τ$ mass unification within this …
In this talk I review the motivations for physics beyond the Standard Model at the TeV scale and the prospects for their detection in the second Run of LHC. Then I focus in the supersymmetric case, paying special attention to the formulation and implications of the Natural SUSY scenario.
We study the implications of LHC searches on SUSY particle spectra using flat scans of the 19-parameter pMSSM phase space. We apply constraints from flavour physics, g_mu-2, dark matter and earlier LEP and Tevatron searches. The sensitivity of the LHC SUSY searches with jets, leptons and missing energy is assessed by reproducing with fast simulation the recent CMS analyses after validation on benchmark points. We present results in terms of the fraction of pMSSM points compatible with all the constraints which are excluded by the LHC searches with 1 fb^{-1} and 15 fb^{-1} as a function of the …
The notion of stringy naturalness-- that an observable O_2 is more natural than O_1 if more (phenomenologically acceptable) vacua solutions lead to O_2 rather than O_1-- is examined within the context of the Standard Model (SM) and various SUSY extensions: CMSSM/mSUGRA, high-scale SUSY and radiatively-driven natural SUSY (RNS). Rather general arguments from string theory suggest a (possibly mild) statistical draw towards vacua with large soft SUSY breaking terms. These vacua must be tempered by an anthropic veto of non-standard vacua or vacua with too large a value of the weak scale m(weak). W…
Recently, WMAP has measured the cosmological parameters to a much greater accuracy. We analyze the implications of this more precise measurement for supersymmetric dark matter and for the direct detection of supersymmetry at accelerators. We consider mSUGRA including also the hyperbolic branch in the radiative breaking of the electroweak symmetry. On the part of the hyperbolic branch where the lightest neutralino is dominantly a higgsino rather than being mostly a bino, the relic density constraints are satisfied by coannihilation with the next lightest neutralino and the light chargino. Inclu…
We discuss the motivations and implications of models of low-energy supersymmetry. We present the case for the minimal supersymmetric standard model, which we define to include the minimal particle content and soft supersymmetry-breaking interactions which are universal at the GUT or Planck scale. This model is in agreement with all present experimental results, and yet depends on only a few unknown parameters and therefore maintains considerable predictive power. From the theoretical side, it arises naturally in the context of supergravity models. We discuss radiative electroweak symmetry bre…
We investigate the Higgs boson sector of the Minimal Supersymmetric Standard Model (MSSM) in the framework of the three most prominent soft SUSY-breaking scenarios, mSUGRA, MGMSB and mAMSB. For each scenario, we determine the parameters at the electroweak scale from the set of input variables at higher energy scales (depending on the specific scenario) and evaluate the Higgs boson properties. The latter are based on results obtained within the Feynman-diagrammatic approach by taking into account the complete one-loop and the dominant two-loop contributions. The maximum value of the mass of the…
Supersymmetry exhibts new sources of CP violation. We discuss the implications of these new contributions to CP violation both in the K and B physics. We show that CP violation puts severe constraints on low energy SUSY, but it represents also a promising ground to look for signals of new physics.
We consider phenomenological implications of susy models with spontaneously broken CP-symmetry. In particular, we analyze CP-asymmetries in B decays and find that the predictions of these models are vastly different from those of the SM. These features are common to NMSSM-like models with an arbitrary number of sterile superfields and the MSSM with broken R-parity.
We present a short review of the LHC results at 7 TeV and their implications on the Standard Model (SM) and on its Supersymmetric (SUSY) extension. In particular we discuss the exclusion range for the SM Higgs mass, the tantalizing hint of an excess at $m_H \sim 125$ GeV, the negative results of searches for SUSY particles (as well as for any other new physics) and the present outlook.
The proton decays too rapidly in supersymmetric theories if a dimension-4 operator \bar{5}.10.\bar{5} exists in the superpotential. The conventional idea is to impose the R-parity to kill this operator with a stable lightest supersymmetry particle (LSP) as a direct consequence. However, the SUSY-zero mechanism is also able to kill the operator without an unbroken R-parity. In this article, we provide a firm theoretical justification for the absence of the dimension-4 proton decay operator under the SUSY-zero mechanism, by using some input from string theory. The LSP may be unstable without the…
We investigate the viability of light neutralino scenarios as promoted by dark matter direct detection experiments. Using high statistics scans in the pMSSM we have identified several scenarios which give rise to very light neutralinos with large direct detection scattering cross sections. Our results are challenged with constraints from dark matter relic density, direct detection, indirect detection, as well as flavour physics, electroweak precision tests, LEP and Tevatron limits, LHC limits on SUSY, Higgs and monojet searches. In particular we study the effect of a Higgs boson in the range 1…
We show that presently available precision data are in good agreement with supersymmetry at a mass scale below 1 TeV. Using a SUSY point close to the best fit to present data, we give a projection of the capabilities of the LHC to constrain SUSY models and their parameters as function of the accumulated luminosity.
In this work we re-examine the correlation between B(d,s)-anti-B(d,s) mixing and Lepton Flavour Violation in the light of recent experimental measurements in the $B_s$ system. We perform a generic SUSY analysis of the allowed down squark mass insertion parameter space. In the SUSY GUT scenario this parameter space is then used to make predictions for LFV branching ratios. We find that the recent measurement for the CP phase $ϕ_s$ excludes the lowest rates for tau --> mu + gamma and provides a lower bound of ~ 3E-9 for tan beta = 10. Future experimental improvements in the bound on tau --> mu +…
We analyze the Higgs intense--coupling regime, in which all Higgs particles of the Minimal Supersymmetric Standard Model are light with masses of the same order and the value of $\tb$ the ratio of vacuum expectation values of the two Higgs fields is large, in the framework of Supergravity scenarios with non--universal soft Supersymmetry breaking scalar masses in the Higgs sector. In particular, we calculate the relic density abundance of the lightest neutralino candidate for cold dark matter and the rates in direct and indirect detection at present and future experiments. We first show that wh…
The plan for mass and spin measurement of SUSY particles with the ATLAS detector is presented. The measurements of kinematical distributions, such as edges in the invariant mass of leptons and jets, could be used to constrain the model of SUSY that may be discovered at the LHC. Examples from a few points in the mSUGRA scenario are provided with an emphasis on measurements that can be conducted within the first few years of data taking.
We consider the phenomenological implications of a soft SUSY breaking term BN at the TeV scale (here B is the U(1)_Y gaugino and N is the right-handed neutrino field). In models with a massless (or nearly massless) neutralino, such a term will give rise through the see-saw mechanism to new contributions to the mass matrix of the light neutrinos. We treat the massless neutralino as an (almost) sterile neutrino and find that its mass depends on the square of the soft SUSY breaking scale, with interesting consequences for neutrino physics. We also show that, although it requires fine-tuning, a ma…
We explore the physics of the general CP-conserving MSSM with Minimal Flavor Violation, the pMSSM. The 19 soft SUSY breaking parameters are chosen so to satisfy all existing experimental and theoretical constraints assuming that the WIMP is the lightest neutralino. We scan this parameter space twice using both flat and log priors and compare the results which yield similar conclusions. Constraints from both LEP and the Tevatron play an important role in obtaining our final model samples. Implications for future TeV-scale $e^+e^-$ linear colliders(LC) are discussed.
We consider supersymmetric (SUSY) models in which a very light gravitino is the lightest SUSY particle. Assuming that a neutralino is the next-to-lightest SUSY particle, we present a measurement of the neutralino mass at the LHC in two photons + missing energy events, which is based on the MT2 method. It is a direct measurement of the neutralino mass itself, independent of other SUSY particle masses and patterns of cascade decays before the neutralino is produced.
The lack of evidence for weak scale supersymmetry from LHC Run-I and Run-II results along with null results from direct/indirect dark matter detection experiment have caused a paradigm shift in expected phenomenology of SUSY models. The SUSY dark matter candidate, neutralino $\widetilde{Z}_1$, can only satisfy the measured dark matter abundance due to resonance- and co-annihilations in cMSSM model. Moreover, viable parameter space is highly fine-tuned in the cMSSM. In models that can still satisfy the naturalness condition such as NUHM2, the neutralino is underproduced due to its higgsino natu…
