No Arabic abstract
Family gauge boson production at the LHC is investigated according to a $U(3)$ family gauge model with twisted family number assignment. In the model we study, a family gauge boson with the lowest mass, $A_1^{ 1}$, interacts only with the first generation leptons and the third generation quarks. (The family numbers are assigned, for example, as $(e_1, e_2, e_3)= (e^-, mu^-, tau^-)$ and $(d_1, d_2, d_3)=(b, d, s) $[or $(d_1, d_2, d_3)=(b, s, d)$]). In the model, the family gauge coupling constant is fixed by relating to the electroweak gauge coupling constant. Thus measurements of production cross sections and branching ratios of $A_1^{ 1}$ clearly confirm or rule out the model. We calculate the cross sections of inclusive $A_1^{ 1}$ production and $b bar{b} , (t bar{t})$ associated $A_1^{ 1}$ production at $sqrt{s} = 14~text{TeV}$ and $100~text{TeV}$. With the dielectron production cross section, we discuss the determination of diagonalizing matrix of quark mass matrix, $U_{u}$ and $U_{d}$, respectively.
Weak gauge boson pair production is an important process at the LHC because it probes the non-Abelian structure of electroweak interactions and it is a background process for many new physics searches, and with enough statistics we can perform comparisons between measurements and theoretical calculations for different but correlated observables. In these proceedings, we present a theoretical status including state-of-the-art results from recent calculations of higher-order QCD and electroweak corrections.
We search for signatures of the extra neutral gauge boson $ Z^prime$, predicted in some extensions of the Standard Model, from the analysis of some distributions for $p + p longrightarrow mu^+ + mu^- + X$, where the only exotic particle involved is $ Z^prime$. In addition to the invariant mass and charge asymmetry distributions, we propose in our search to use the transverse momentum distribution ($p_T$) as an observable. We do our calculation for two values of the LHC center of mass energy (7 and 14 TeV), corresponding to 1 and 100 fb$^{-1}$ of luminosity, in order to compare our findings from some models with the distributions following from the Standard Model. By applying convenient cuts in the invariant mass, we show that the final particles $p_T$ distributions can reveal the presence of an extra neutral gauge boson contribution. We also claim that it is possible to disentangle the models considered here and we emphasize that the minimal version of the model, based on ${SU (3)_C times SU (3)_L times U (1)_X}$ symmetry, presents the more clear signatures for $ Z^prime$ existence.
We study the single production of the fourth family quarks through the process pp--> QjX at the Large Hadron Collider (LHC). We have calculated the decay widths and branching ratios of the fourth family quarks (b and t) in the mass range 300-800 GeV. The cross sections of signal and background processes have been calculated in a Monte Carlo framework. It is shown that the LHC can discover single t and b quarks if the CKM matrix elements |V_{tq}|,|V_{qb}|>=0.01.
For the purpose of cross-fertilising currently separate experimental approaches, we connect results of LHC analyses attempting to access the properties of additional $W^prime$ and $Z^prime$ bosons from Drell-Yan processes. Under theoretical assumptions linking the two new gauge bosons, we take into account that such possible states of nature are wide enough (in relation to the leptonic mass resolution) for the corresponding signals be significantly affected by interference effects with the background from the Standard Model. The shape of the differential cross section may then no longer be a standard Breit-Wigner distribution, and asymmetry observables would become useful for characterisation (and, possibly, discovery) purposes. Under such conditions we concentrate our analysis on specific widely-studied models: the Sequential Standard Model, a model with an additional $SU(2)_L$ gauge symmetry, as well as standard and alternative realisations of the Left-Right Symmetric Model. We show how information gathered in $Z$ boson searches in terms of cross section and/or asymmetry distributions can be used to improve $W$ boson searches in terms of the LHC sensitivity, and {it vice versa}.
Triple gauge boson associated production at the LHC serves as an interesting channel to test the robustness of the Standard Model. Any deviation from its SM prediction may indicate possible existence of relevant new physics, e.g., anomalous quartic gauge boson couplings. In this paper, a Monte-Carlo feasibility study of measuring WWA production with pure leptonic decays and probing anomalous quartic gauge-boson (e.g., WWAA) couplings, is presented in detail for the first time, with parton shower and detector simulation effects taken into account. Our results show that at the sqrt{s} = 14 TeV LHC with an integrated luminosity of 100 (30) fb-1, one can reach a significance of 9 (5) sigma to observe the SM WWA production, and can constrain at the 95% CL the anomalous WWAA coupling parameters, e.g., a_{0,c}^W/Lambda^2 (see Ref.[15] for their definitions), at 10^{-5} GeV^{-2}, respectively.