119221476
Same-sign tops: a powerful diagnostic test for models of new physics
A bstractWe study the connection between the same sign top (SST) and the top quark forward-backward asymmetry $ \left( {\mathcal{A}_{\mathrm{FB}}^t} \right) $. We find that a large class of new physics (NP) models that have been proposed to account for the $ \mathcal{A}_{\mathrm{FB}}^t $ lead to SST quark production rate much larger than the observed rate at the LHC and consequently are severely constrained or ruled out. Our model independent, general, operator analysis shows that none of the tree- level self-conjugate flavor-changing operators are able to explain $ \mathcal{A}_{\mathrm{FB}}^t $ and simultaneously remain consistent with the same-sign top-quark production constraints from the LHC data.
197440770
CP violating anomalous top-quark couplings at the Large Hadron Collider
In this talk, I review the T-odd correlations induced by CP violating anomalous top-quark couplings at both production and decay level in the process gg --> t t_bar --> (b mu+ nu_mu) (b_bar mu-nu_mu_bar). In addition I will also focus on experimental sensitivities corresponding to the anomalous couplings at the LHC.
207846098
Right sneutrinos in a supergravity model and the signals of a stable stop at the Large Hadron Collider
119107758
Peccei-Quinn violating minimal supergravity and a 126 GeV Higgs boson
In a Peccei-Quinn extension of supergravity the h --> \gamma\gamma detection rate can be significantly enhanced due to the reduction of the total Higgs decay width. To assess the viability of various Peccei-Quinn extensions of minimal supergravity we perform a Bayesian analysis on three such scenarios. The main constraints on these models come from the currently observed Higgs boson like state by the Large Hadron Collider and from the WMAP observation of dark matter abundance. Our comparative study reveals that under these constraints the PQ violating scenarios with axino dark matter are clearly preferred over the minimal supegravity model with the lightest neutralino as a dark matter candidate.
14302099
Right-chiral sneutrinos and long-lived staus: Event characteristics at the CERN Large Hadron Collider
We investigate the signals of a supersymmetric scenario where the lighter tau-sneutrino is the lightest supersymmetric particle, while the lighter stau-state is the next lightest. We confirm that such a scenario can be motivated within the framework of minimal supergravity, with just the addition of a right-chiral neutrino superfield. Such a spectrum leads to rather unusual signals of supersymmetry, showing stable tracks of the stau in the muon chambers. We have studied two types of signals, namely (a) two or more hard jets and two stau tracks, and (b) hard jets with two muons and two stau tracks. We demonstrate that the stau tracks can be distinguished from the muonic ones through proper kinematic cuts which also enable one to remove all standard model backgrounds.
8775045
The Impossibility of heavy neutrino dark matter in the Littlest Higgs Model with T-parity: Constraints from direct search
We consider the Littlest Higgs Model with T-parity (LHT), in the parameter region where a heavy neutrino is the lightest T-odd particle (LTP). Having emphasized that this corresponds to a sizable region in the parameter space of the theory, we show that both the Cryogenic Dark Matter Search (CDMS) and Xenon10 experiments disallow the entire region where the masses of the new particles in LHT can lie within several TeV. Therefore, any observation of the signals of a heavy neutrino LTP is likely to seriously reopen the issue of cold dark matter in the universe.
35885424
Stabilizing hadron resonance gas models
We examine the stability of hadron resonance gas models by extending them to include undiscovered resonances through the Hagedorn formula. We find that the influence of unknown resonances on thermodynamics is large but bounded. We model the decays of resonances and investigate the ratios of particle yields in heavy-ion collisions. We find that observables such as hydrodynamics and hadron yield ratios change little upon extending the model. As a result, heavy-ion collisions at the RHIC and LHC are insensitive to a possible exponential rise in the hadronic density of states, thus increasing the stability of the predictions of hadron resonance gas models in this context. Hadron resonance gases are internally consistent up to a temperature higher than the crossover temperature in QCD, but by examining quark number susceptibilities we find that their region of applicability ends below the QCD crossover.
123580970
Implication of the EMC-effect on high transverse momentum jets
We show that the extension of nuclear structure functions to the regionx>1 can give rise to an enhancement of high-pT jet cross sections in hadron nucleus collisions. Such extensions are expected in a class of models proposed to explain the EMC-effect. Since these models are completely parametrized by the deep inelastic scattering data, the jet cross section emerge as parameter free predictions.
14798493
Effects of momentum-dependent symmetry potential on heavy-ion collisions induced by neutron-rich nuclei
Abstract Using an isospin- and momentum-dependent transport model we study effects of the momentum-dependent symmetry potential on heavy-ion collisions induced by neutron-rich nuclei. It is found that symmetry potentials with and without the momentum-dependence but corresponding to the same density-dependent symmetry energy E sym ( ρ ) lead to significantly different predictions on several E sym ( ρ )-sensitive experimental observables especially for energetic nucleons. The momentum- and density-dependence of the symmetry potential have to be determined simultaneously in order to extract the E sym ( ρ ) accurately. The isospin asymmetry of midrapidity nucleons at high transverse momenta is particularly sensitive to the momentum-dependence of the symmetry potential. It is thus very useful for investigating accurately the equation of state of dense neutron-rich matter.
10127072
Phenomenological Analysis of Hybrid Textures of Neutrinos
Abstract We present a comprehensive phenomenological analysis of the allowed hybrid textures of neutrinos. Out of a total of sixty hybrid textures with one equality between the elements of neutrino mass matrix and one texture zero only twenty three are found to be viable at 99% C.L. whereas the earlier analysis found fifty four to be viable. We examine the phenomenological implications of the allowed hybrid textures including Majorana type CP-violating phases, 1–3 mixing angle and Dirac type CP-violating phase, δ. We, also, obtain lower bound on effective Majorana mass for all the allowed hybrid textures.
119638891
Delayed energetic events in extensive air showers
Production of massive (> or =10 GeV/c/sup 2/) strongly interacting particles in very-high-energy interactions has been suggested by many theories. These particles, if produced in the cores of extensive air showers in the upper atmosphere, would arrive at the observational level delayed by tens of nanoseconds relative to all other known particles of similar energy, provided they are relatively stable (lifetime >10/sup -6/ s). Experiments searching for such particles have reported observing delayed (>20 ns) energetic (>40 GeV) events. However several anomalous features observed for these events have precluded their interpretation in terms of massive particles with ordinary hadronic interaction characteristics in a conclusive manner. We report here the details of a new experiment carried out at the Ooty laboratory during 1978--1981 where we have attempted to study the delayed energetic events with a multidetector system placed inside the large Ooty multiplate cloud chamber. Our observations show that the delayed energetic events could not be ascribed to high-energy hadronlike interactions of a massive strongly interacting particle. We have observed one delayed event showing a high-energy cascade in cloud chamber but inadequate timing information does not make a convincing case for this event to be due to a high-energy delayed massivemore » hadron. However this event combined with observation of two similar events earlier by Tonwar et al. suggest the existence of some interesting phenomenon requiring observations over a long period of time. We have obtained a 99% C.L. upper limit of 1.7 x 10/sup -11/ cm/sup -2/ s/sup -1/ sr/sup -1/ for the flux of massive particles in extensive air showers of size approx.(5 x 10/sup 4/)--(5 x 10/sup 6/) particles which corresponds to an upper limit of 2.5 x 10/sup -33/ cm/sup 2/ for the production cross section for particles of mass >10 GeV/c/sup 2/ at energies of approx.10/sup 5/--10/sup 7/ GeV.« less