5,377 research outputs found

    Associated neutralino-neutralino-photon production at NLC

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    We study the potential of an e+ee^+e^- linear collider to search for neutralino-neutralino-photon production. Our analysis shows that this signal is not viable under realistic expectations for electron beam polarization due to large Standard Model backgrounds. Such a search would be possible only if beam polarizations of near 100% could be achieved.Comment: 3 pages, 6 figures, uses RevTeX4. Contribution to Snowmass 200

    Forward-Backward Asymmetry as a Discovery Tool for Z' Bosons at the LHC

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    The Forward-Backward Asymmetry (AFB) in Z' physics is commonly only perceived as the observable which possibly allows one to interpret a Z' signal by distinguishing different models of such (heavy) spin-1 bosons. In this paper, we examine the potential of AFB in setting bounds on or even discovering a Z' boson at the Large Hadron Collider (LHC) and show that it might be a powerful tool for this purpose. We analyse two different scenarios: Z' bosons with a narrow and wide width, respectively. We find that, in the first case, the significance of the AFB search can be comparable with that of the bump search usually adopted by the experimental collaborations; however, being a ratio of (differential) cross sections the AFB has the advantage of reducing systematical errors. In the second case, the AFB search can win over the bump search in terms of event shape, as the structure of the AFB distribution as a function of the invariant mass of the reconstructed Z'boson could nail down the new broad resonance much better than the event counting strategy usually adopted in such cases.Comment: 27 pages, 17 figure

    Exploring neutralino dark matter resonance annihilation via bA,bH -> b mu^+ mu^- at the LHC

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    One of the main channels which allows for a large rate of neutralino dark matter annihilation in the early Universe is via the pseudoscalar Higgs A-resonance. In this case, the measured dark matter abundance can be obtained in the minimal supergravity (mSUGRA) model when tan(beta)\sim 50 and 2m_{\tz_1}\sim m_A. We investigate the reaction pp\to b\phi\to b\mu^+\mu^- +X (where \phi =A or H) at the CERN LHC where requiring the tag of a single b-jet allows for amplification of the signal-to-background ratio. The rare but observable Higgs decay to muon pairs allows for a precise measurement of the Higgs boson mass and decay width. We evaluate signal and background using CalcHEP, with muon energy smearing according to the CMS detector. We find that the Higgs width (\Gamma_A) can typically be determined with the accuracy up to \sim 8% (\sim 17%) for m_A\sim 400 (600) GeV assuming 10^3 fb^{-1} of integrated luminosity. Therefore, the pp\to b\phi\to b\mu^+\mu^- +X process provides a unique possibility for direct \Gamma_A measurement at the LHC. While the Higgs width is correlated with the parameter \tan\beta for a given value of m_A, extracting \tan\beta is complicated by an overlap of the A and H peaks, radiative corrections to the b and \tau Yukawa couplings, and the possibility that SUSY decay modes of the Higgs may be open. In the case where a dilepton mass edge from \tz_2\to\ell^+\ell^-\tz_1 is visible, it should be possible to test the relation that 2m_{\tz_1}\sim m_A.Comment: 19 pages with 25 .eps figure