No Arabic abstract
This paper examines the transverse momentum spectra of hadrons in the multiparticle production at LHC in the framework of the Quark-Gluon String Model (QGSM). It discusses the dependence of average pt on the masses of mesons and baryons at the LHC energy 7 TeV. The QGSM description of the experimental spectra of various hadrons led to the number of conclusions. I. The average transverse momenta of baryons and mesons are growing with the hadron mass and for beauty hadrons, they are almost equal to the mass. II. By the product of research, a regularity has been detected in the mass gaps between hadron generations. This hypothesis suggests some hidden symmetrical (neither-meson-nor-baryon) neutral hadron states with the masses: 0.251,0.682,1.85,5.04,13.7,37.2,101.,275.,748.... GeV, which is produced by geometrical progression with the mass factor of order delta(ln M)=1. III. The baryon-meson symmetry seems broken until the mass of beauty hadrons, then the hidden states should be more and more stable with the growth of the mass, so the suggested sequence of hadronic states is a proper candidate for the Dark Matter that, you know, contributes the valuable part to the mass of Universe. The growing average transverse momenta are extrapolated with a similar function, as for energy dependence of average baryon pt, < pt > ~ M**0.1.
A heavy Standard Model Higgs boson is not only disfavored by electroweak precision observables but is also excluded by direct searches at the 7 TeV LHC for a wide range of masses. Here, we examine scenarios where a heavy Higgs boson can be made consistent with both the indirect constraints and the direct null searches by adding only one new particle beyond the Standard Model. This new particle should be a weak multiplet in order to have additional contributions to the oblique parameters. If it is a color singlet, we find that a heavy Higgs with an intermediate mass of 200 - 300 GeV can decay into the new states, suppressing the branching ratios for the standard model modes, and thus hiding a heavy Higgs at the LHC. If the new particle is also charged under QCD, the Higgs production cross section from gluon fusion can be reduced significantly due to the new colored particle one-loop contribution. Current collider constraints on the new particles allow for viable parameter space to exist in order to hide a heavy Higgs boson. We categorize the general signatures of these new particles, identify favored regions of their parameter space and point out that discovering or excluding them at the LHC can provide important indirect information for a heavy Higgs. Finally, for a very heavy Higgs boson, beyond the search limit at the 7 TeV LHC, we discuss three additional scenarios where models would be consistent with electroweak precision tests: including an additional vector-like fermion mixing with the top quark, adding another U(1) gauge boson and modifying triple-gauge boson couplings.
This paper examines the transverse momentum spectra of baryons in the multi-particle production at modern colliders using Quark-Gluon String Model (QGSM). It discusses 1) the difference in Lambda^0 hyperon spectra at antiproton-proton vs. proton-proton reactions; 2) the growth of average transverse momenta of Lambda hyperon with proton-proton collision energies and 3) the dependence of average p_t on the masses of mesons and baryons at the LHC energy 7 TeV. This analysis of baryon spectra led to the following conclusions. First, the fragmentation of antidiquark-diquark side of the pomeron diagram makes the major contribution to baryon production spectra in the asymmetric antiproton-proton reaction. Second, the average p_ts of hyperons steadily grow with energy on the range from 53 GeV to 7 TeV. Since no dramatic changes were seen in the characteristics of baryon production, the hadroproduction processes do not cause the knee in the cosmic ray proton spectra at the energies between Tevatron and LHC.
The transverse momentum distributions of various hadrons produced in most central Pb+Pb collisions at LHC energy Root(s_NN) = 2.76 TeV have been studied using our earlier proposed unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment. The model calculation fits provide the thermal freeze-out conditions in terms of the temperature and collective flow effect parameters for different particle species. Interestingly the model parameter fits reveal a strong collective flow in the system which appears to be a consequence of the increasing particle density at LHC. The model used incorporates a longitudinal as well as transverse hydrodynamic flow. The chemical potential has been assumed to be nearly equal to zero for the bulk of the matter owing to a high degree of nuclear transparency effect at such energies. The contributions from heavier decay resonances are also taken into account in our calculations.
The 19/20-parameter p(henomenological)MSSM with either a neutralino or gravitino LSP offers a flexible framework for the study of a wide variety of R-parity conserving MSSM SUSY phenomena at the 7, 8 and 14 TeV LHC. Here we present the results of a study of SUSY signatures at these facilities obtained via a fast Monte Carlo replication of the ATLAS SUSY analysis suite. In particular, we show the ranges of the sparticle masses that are either disfavored or remain viable after all of the various searches at the 7 and 8 TeV runs are combined. We then extrapolate to 14 TeV with both 300 fb^-1 and 3 ab^-1 of integrated luminosity and determine the sensitivity of a jets + MET search to the pMSSM parameter space. We find that the high-luminosity LHC performs extremely well in probing natural SUSY models.
We present a study of transverse momentum ($p_{T}$) spectra of unidentified charged particles in pp collisions at RHIC and LHC energies from $sqrt{s}$ = 62.4 GeV to 13 TeV using Tsallis/Hagedorn function. The power law of Tsallis/Hagedorn form gives excellent description of the hadron spectra in $p_{T}$ range from 0.2 to 300 GeV/$c$. The power index $n$ of the $p_T$ distributions is found to follow a function of the type $a+b/sqrt {s}$ with asymptotic value $a = 5.72$. The parameter $T$ governing the soft bulk contribution to the spectra remains almost same over wide range of collision energies. We also provide a Tsallis/Hagedorn fit to the $p_{T}$ spectra of hadrons in pPb and different centralities of PbPb collisions at $sqrt{s_{NN}}$ = 5.02 TeV. The data/fit shows deviations from the Tsallis distribution which become more pronounced as the system size increases. We suggest simple modifications in the Tsallis/Hagedorn power law function and show that the above deviations can be attributed to the transverse flow in low $p_T$ region and to the in-medium energy loss in high $p_T$ region.