共查询到20条相似文献,搜索用时 125 毫秒
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Peiying Li Gongru Lu Jin Min Yang Huanjun Zhang 《The European Physical Journal C - Particles and Fields》2007,51(1):163-168
In the minimal supersymmetric standard model the R-parity violating interactions can induce anomalous top pair productions
at the LHC through the t-channel process dRd̄R→tLt̄L by exchanging a slepton or by the u-channel process dRd̄R→tRt̄R exchanging a squark. Such top pair productions with a certain chirality cause top-quark polarization in the top pair events.
We found that at the LHC, due to the large statistics, the statistical significance of the polarization observable, and thus
the probing ability for the corresponding R-parity violating couplings, is much higher than at the Tevatron upgrade.
PACS 14.65.Ha; 14.80.Ly 相似文献
12.
C. Degrande J.-M. GérardC. Grojean F. MaltoniG. Servant 《Physics letters. [Part B]》2011,703(3):306-309
We study the phenomenology of same sign top pair production at the LHC in a model-independent way. The complete set of dimension six operators involving two top (or anti-top) quarks is introduced and the connection with all possible t- or s-channel heavy particle exchanges is established. Only in the former case, same and opposite sign top pair production can be related. We find that while current Tevatron data disfavor t-channel models, other production mechanisms are viable and can be tested at the LHC. 相似文献
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WANG Xue-Lei LI Ji-Tao LIU Su-Zhen 《理论物理通讯》2007,48(5):891-894
In the minimal supersymmetric standard model with R-parity violation, the lepton number violating top quark interactions can contribute to the top pair production at a linear collider via tree-level u-channel squark exchange diagrams. We calculate such contributions and find that in the allowed range of these R-violating couplings, the top pair production rate as well as the top quark polarization and the forward-backward asymmetry can be significantly altered. By comparing the unpolarized beams with the polarized beams, we find that the polarized beams are more powerful in probing such new physics. 相似文献
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Nikolaos Kidonakis 《Physics of Particles and Nuclei》2014,45(4):714-722
I discuss threshold resummation at NNLL accuracy in the standard moment-space approach in perturbative QCD for top-pair and single-top production. For top quark pair production I present new approximate NNLO results for the total cross section and for the top quark transverse momentum and rapidity distributions at 8 TeV LHC energy. I discuss the accuracy of the soft-gluon approximation and show that the NLO and NNLO approximate results from resummation are practically indistinguishable from exact NLO and partial NNLO results. For single top production I present new approximate NNLO results for the total cross sections in all three channels at the LHC and also for the top quark transverse momentum distributions in t-channel production and in top-quark associated production with a W boson. For both \(t\bar t\) and single-top production the agreement of theoretical results with LHC and Tevatron data is excellent. 相似文献
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Ashutosh Kumar Alok Sudhir Kumar Gupta 《The European Physical Journal C - Particles and Fields》2010,65(3-4):491-500
We study B s →μ + μ ? in the context of the R-parity violating minimal supergravity in the high-tan?β regime. We find that the lowest value of the branching ratio can go well below the present LHCb sensitivity and hence B s →μ + μ ? can even be invisible to the LHC. We also find that the present upper bound on Br?(B s →μ + μ ?) puts strong constraint on the minimal supergravity parameter space. The constraints become more severe if the upper bound is close to its standard model prediction. 相似文献
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M. Khatiri Yanehsari S. Jafari M. Mohammadi Najafabadi 《International Journal of Theoretical Physics》2013,52(11):4229-4236
We study the possibility of production of same sign top quark pairs at the LHC as a direct probe of flavor changing neutral current (FCNC) processes in the tqg vertices. In particular, the LHC potential to probe the flavor violating parameter κ/Λ is investigated with 5, 10, 15, and 20 fb?1 of integrated luminosity of data of 7 and 8 TeV collisions. We find that the LHC can probe it down to 0.13 TeV?1 via double top production process. Also, we examine the effects of variation of factorization scale and different parton distribution functions on the total cross section of same sign top quark pair at the LHC. The results could be a valid starting point for a more detailed experimental study. 相似文献
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JYOTHSNA RANI KOMARAGIRI 《Pramana》2012,79(5):1223-1226
The measurement of t-channel single top cross-section in proton?Cproton collisions at the Large Hadron Collider (LHC) at a centre-of-mass energy of 7 TeV, using data collected with the Compact Muon Solenoid (CMS) experiment during the year 2010 is presented. Both the electron-neutrino and muon-neutrino decay channels of W boson from top decay are considered. Two complementary multivariate analysis methods to separate signal and background and to extract the cross-section for the single top produced in t-channel are explored. The result is compared with the most precise Standard Model theory predictions. 相似文献
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Sujoy Poddar 《Pramana》2007,69(5):839-842
In a R-parity violating (RPV) model of neutrino mass with three bilinear couplings μ
i
and three trilinear couplings λ′
i33, where i is the lepton index, we find six generic scenarios each with a distinctive pattern of the trilinear couplings consistent
with the neutrino oscillation data. These patterns may be reflected in direct RPV decays of the lighter top squark or in the
RPV decays of the lightest superparticle, assumed to be the lightest neutralino. Typical signal sizes at the Tevatron RUN
II and the LHC have been estimated and the results turn out to be encouraging.
相似文献
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In the supersymmetric standard model of particle interactions, R-parity nonconservation is often invoked to obtain nonzero neutrino masses. We point out here that such interactions of the supersymmetric particles would erase any pre-existing lepton or baryon asymmetry of the universe before the electroweak phase transition through the B+L violating sphaleron processes. We also point out that all models of radiative generation of neutrino masses suffer from the same problem. We then show how neutrino masses may be obtained in supersymmetry (assuming R-parity conservation) together with successful leptogenesis and predict the possible existence of new observable particles. 相似文献
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A study of energy behavior of the pion spectra and interferometry scales is carried out for the top SPS, RHIC and for LHC
energies within the hydrokinetic approach. The main mechanisms that lead to the paradoxical, at first sight, dependence of
the interferometry scales with an energy growth, in particular, a decrease R
out/R
side ratio, are exposed. The hydrokinetic predictions for the HBT radii at LHC energies are compared with the recent results of
the ALICE experiment. 相似文献