54573705
Constraints on the $R$-parity violating minimal supersymmetric standard model with neutrino masses from multilepton studies at the LHC
In a recent paper, we proposed a hierarchical ansatz for the lepton-number-violating trilinear Yukawa couplings of the R-parity violating minimal supersymmetric standard model. As a result, the number of free parameters in the lepton-number-violating sector was reduced from 36 to 6. Neutrino oscillation data fixes these six parameters, which also uniquely determines the decay modes of the lightest supersymmetric particle and thus governs the collider signature at the LHC. A typical signature of our model consists of multiple leptons in the final state and significantly reduced missing transverse momentum compared to models with R-parity conservation. In this work, we present exclusion limits on our model based on multilepton searches performed at the Large Hadron Collider with 7 TeV center-of-mass energy in 2011 while accommodating a 125 GeV Higgs.
53580211
The higgsino–singlino world at the large hadron collider
We consider light higgsinos and singlinos in the next-to-minimal supersymmetric standard model at the large hadron collider. We assume that the singlino is the lightest supersymmetric particle and that the higgsino is the next-to-lightest supersymmetric particle with the remaining supersymmetric particles in the multi-TeV range. This scenario, which is motivated by the flavor and CP issues, provides a phenomenologically viable dark matter candidate and improved electroweak fit consistent with the measured Higgs mass. Here, the higgsinos decay into on (off)-shell gauge boson and the singlino. We consider the leptonic decay modes and the resulting signature is three isolated leptons and missing transverse energy which is known as the trilepton signal. We simulate the signal and the Standard Model backgrounds and present the exclusion region in the higgsino–singlino mass plane at the large hadron collider at $$\sqrt{s}=14$$s=14 TeV for an integrated luminosity of 300 fb$$^{-1}$$-1.
14458517
Rapidity Gap Events in Squark Pair Production at the LHC
The exchange of electroweak gauginos in the t− or u−channel allows squark pair production at hadron colliders without color exchange between the squarks. This can give rise to events where little or no energy is deposited in the detector between the squark decay products. We discuss the potential for detection of such rapidity gap events at the Large Hadron Collider (LHC). Our numerical analysis is divided into two parts. First, we evaluate in a simplified framework the rapidity gap signal at the parton level. The second part covers an analysis with full event simulation using PYTHIA as well as Herwig++, but without detector simulation. We analyze the transverse energy deposited between the jets from squark decay, as well as the probability of finding a third jet in between the two hardest jets. For the mSUGRA benchmark point SPS1a we find statistically significant evidence for a color singlet exchange contribution. The systematical differences between current versions of PYTHIA and HERWIG++ are larger than the physical effect from color singlet exchange; however, these systematic differences could be reduced by tuning both Monte Carlo generators on normal QCD di–jet data.
118182564
A Simple Baryon Triality Model for Neutrino Masses
We make a simple ansatz for the supersymmetric lepton-number violating Yukawa couplings, by relating them to the corresponding Higgs Yukawa couplings. This reduces the free B$_3$ parameters from 36 to 6. We fit these parameters to solve the solar and atmospheric neutrino anomalies in terms of neutrino oscillations. The resulting couplings are consistent with the stringent low-energy bounds. We investigate the resulting LHC collider signals for a stau LSP scenario.
119259465
‘Stop’ that ambulance! New physics at the LHC?
A bstractA number of LHC searches now display intriguing excesses. Most prominently, the measurement of the W+W− cross-section has been consistently ∼ 20% higher than the theoretical prediction across both ATLAS and CMS for both 7 and 8 TeV runs. More recently, supersymmetric searches for final states containing two or three leptons have also seen more events than predicted in certain signal regions. We show that a supersymmetric model containing a light stop, winos and binos can consistently match the data. We perform a fit to all measurements and searches that may be sensitive to our model and find a reduction in the log-likelihood of 15.4 compared to the Standard Model which corresponds to 3.5-σ once the extra degrees of freedom in the fit are considered.
14834509
Electroweak Contributions to Squark Pair Production
We compute electroweak contributions to the production of squark pairs at hadron colliders. These include the exchange of electroweak gauge bosons in the $s-$channel as well as electroweak gaugino exchange in the $t-$ and/or $u-$channel. In many cases these can interfere with the dominant QCD contributions. As a result, we find sizable contributions to the production of two SU(2) doublet squarks. At the LHC, they amount to 10 to 20% for typical mSUGRA (or CMSSM) scenarios, but in more general scenarios they can vary between -40 and $+55%$, depending on size and sign of the SU(2) gaugino mass. The electroweak contribution to the total squark pair production rate at the LHC is about 3.5 times smaller.
118141211
Parametrization of the CKM matrix
Noting the hierarchy between three mixing angles, $\theta_{2,3}={\cal O}(\theta_1^2)$, we present an exact form of the quark mixing matrix, replacing Wolfenstein's approximate form. In addition, we suggest to rotate the unitarity triangle, using the weak CP phase convention where the phase is located at the (31) element $\sin\theta_1\sin\theta_2 e^{i\delta}$ while the (13) element $\sin\theta_1\sin\theta_3$ is real. For the $(ab)$ unitarity triangle, the base line (x-axis) is defined from the product of the first row elements, $V_{1a}V^*_{1b}$, and the angle between two sides at the origin is defined to be the phase $\delta$. This is a useful definition since every Jarlskog triangle has the angle $\delta$ at the origin, defined directly from the unitarity condition. It is argued that $\delta$ represents the barometer of the weak CP violation, which can be used to relate it to possible Yukawa textures.
119193683
Z' from SU(6)$\times$SU(2)_h GUT, Wjj anomaly and Higgs boson mass bound
A general electroweak scale Z′ is applied in a supersymmetric SU(6)×SU(2)h grand unification model, to have a Z6 for the hexality. We briefly show that there cannot exist any baryonic U(1) ′ B in any subgroup of E6. Any effect that requires sizable Z ′ couplings to quarks like the reported Wjj anomaly of CDF, if observed, implies a substantial Z′ coupling to leptons or Higgs doublets. The kinetic mixing considered in a supersymmetric model from E6 is restricted by the gauge coupling unification and neutrino mixing. The mass of Z′ is strongly constrained by the electroweak ρ0 parameter. We conclude that Z′ mass much above 10 TeV is favored by considering the neutrino mixing and proton decay constraint in supersymmetric models. In this sense, the CDF Wjj anomaly cannot be fitted to any electroweak model descending from E6. Furthermore, if Z ′ is found at several hundred GeV, any grand unification group embedded in E6 such as SU(6)×SU(2), SO(10), SU(5)×U(1), SU(5), SU(4)×SU(4), and SU(3), needs fine-tuned gauge couplings. We also discuss the U(1)′ effect on the tree level mass of the lightest MSSM Higgs boson.
120800011
A common scale for the invisible axion, local SUSY GUTs and Saxino decay
Abstract We identify the scale 10 11–12 GeV as that of the invisible axion and the SUSY breaking scale of local SUSY GUTs. The saxino ( a SUSY partner of the axino; the other partner is the invisble axion) decay is also commented on.
18138135
Neutrino masses from discrete gauge symmetries
Abstract We investigate a model with an extra Z 2 gauge symmetry in the Standard Model. The symmetry gives a structure to the mass matrix for the neutrinos. With two extra Higgs singlets and two extra singlet right-handed neutrinos we can build a model that fits the requirements of the MSW solution of the Solar neutrino problem. With a third singlet right-handed neutrino it is also possible to have a 10 eV neutrino.
118877558
QCD axion and quintessential axion
The axion solution of the strong CP problem is reviewed together with the other strong CP solutions. We also point out the quintessential axion(quintaxion) whose potential can be extremely flat due to the tiny ratio of the hidden sector quark mass and the intermediate hidden sector scale. The quintaxion candidates are supposed to be the string theory axions, the model independent or the model dependent axions.