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Register a new userA New SUSY mass reconstruction method at the CERN LHC
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We propose a new mass reconstruction technique for SUSY processes at the LHC. The idea is to completely solve the kinematics of the SUSY cascade decay by using the assumption that the selected events satisfy the same mass shell conditions of the sparticles involved in the cascade decay. Using this technique, we study the measurement of the mass of the bottom squarks in the cascade decay of the gluino. Based on the final state including two high p_T leptons and two b-jets, we investigate different possible approaches to the mass reconstruction of the gluino and the two bottom squarks. In particular we evaluate the performance of different algorithms in discriminating two bottom squark states with a mass difference as low as 5%.
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When several sparticle masses are known, the kinematics of SUSY decay processes observed at the LHC can be solved if the cascade decays contain sufficient steps. We demonstrate four examples of this full reconstruction technique applied to channels involving leptons, namely a) gluino mass determination, b) sbottom mass determination, c) LSP momentum reconstruction, and d) heavy higgs mass determination.
TeV scale new Physics, e.g., Large Extra Dimensions or Models with anomalous triple vector boson couplings, can lead to excesses in various kinematic regions on the semi-leptonic productions of pp -> WW -> lvjj at the CERN LHC, which, although suffers from large QCD background compared with the pure leptonic channel, can benefit from larger production rates and the reconstructable 4-body mass Mlvjj. We study the search sensitivity through the lvjj channel at the 7TeV LHC on relevant new physics, via probing the hard tails on the reconstructed Mlvjj and the transverse momentum of W-boson (PTW), taking into account main backgrounds and including the parton shower and detector simulation effects. Our results show that with integrated luminosity of 5fb-1, the LHC can already discovery or exclude a large parameter region of the new physics, e.g., 95% CL. limit can be set on the Large Extra Dimensions with a cut-off scale up to 1.5 TeV, and the WWZ anomalous coupling down to, e.g. |lambda_Z|~0.1. Brief results are also given for the 8TeV LHC.
Weak-scale supersymmetry remains to be one of the best-motivated theories of physics beyond the Standard Model. We evaluate the sensitivities of the High Luminosity (HL) and High Energy (HE) upgrades of the LHC to gluinos and stops, decaying through the simplified topologies $tilde{g} to q bar{q} chi^0$, $tilde{g} to t bar{t} chi^0$ and $tilde{t} to t tilde{chi}^0$. Our HL-LHC analyses improve on existing experimental projections by optimizing the acceptance of kinematic variables. The HE-LHC studies represent the first 27 TeV analyses. We find that the HL-(HE-)LHC with 3 ab$^{-1}$ (15 ab$^{-1}$) of integrated luminosity will be sensitive to the masses of gluinos and stops at 3.2 (5.7) TeV and 1.5 (2.7) TeV, respectively, decaying to massless neutralinos.
LHC is expected to be a top quark factory. If the fundamental Planck scale is near a TeV, then we also expect the top quarks to be produced from black holes via Hawking radiation. In this paper we calculate the cross sections for top quark production from black holes at the LHC and compare it with the direct top quark cross section via parton fusion processes at next-to-next-to-leading order (NNLO). We find that the top quark production from black holes can be larger or smaller than the pQCD predictions at NNLO depending upon the Planck mass and black hole mass. Hence the observation of very high rates for massive particle production (top quarks, higgs or supersymmetry) at the LHC may be an useful signature for black hole production.
If the fundamental Planck scale is near a TeV, then we should expect to see TeV scale black holes at the LHC. Similarly, if the scale of supersymmetry breaking is sufficiently low, then we might expect to see light supersymmetric particles in the next generation of colliders. If the mass of the supersymmetric particle is of order a TeV and is comparable to the temperature of a typical TeV scale black hole, then such sparticles will be copiously produced via Hawking radiation: The black hole will act as a resonance for sparticles, among other things. In this paper we compared various signatures for SUSY production at LHC, and we contrasted the situation where the sparticles are produced directly via parton fusion processes with the situation where they are produced indirectly through black hole resonances. We found that black hole resonances provide a larger source for heavy mass SUSY (squark and gluino) production than the direct pQCD-SUSY production via parton fusion processes depending on the values of the Planck mass and blackhole mass. Hence black hole production at LHC may indirectly act as a dominant channel for SUSY production. We also found that the differential cross section dsigma/dp_t for SUSY production increases as a function of the p_t (up to p_t equal to about 1 TeV or more) of the SUSY particles (squarks and gluinos), which is in sharp contrast with the pQCD predictions where the differential cross section dsigma/dp_t decreases as p_t increases for high p_t about 1 TeV or higher. This is a feature for any particle emission from TeV scale blackhole as long as the temperature of the blackhole is very high (~ TeV). Hence measurement of increase of dsigma/dp_t with p_t for p_t up to about 1 TeV or higher for final state particles might be a useful signature for blackhole production at LHC.
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