Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAnalysis and implications of precision near-forward TOTEM data
56
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Very precise data on elastic proton-proton scattering at $sqrt{s}=7$, $8$ and $13$ TeV have been obtained by the TOTEM group at LHC in the near-forward region (momentum transfers down to $|t| = 6 times 10^{-4} {rm GeV}^2$ at $sqrt{s}=8$ TeV and to $|t| = 8 times 10^{-4} {rm GeV}^2$ at $sqrt{s}=13$ TeV). The Coulomb-nuclear interference has been measured with sufficient accuracy for TOTEM to establish the falloff of the $rho$ parameter with increasing energy. The predictions from a previously studied model are shown to be in good agreement with the data and thus allow us to draw rather firm conclusions about the structure of the near-forward nuclear amplitude. We point out that due to a zero in the real part of the nuclear amplitude occurring at a very small momentum transfer--that can migrate into the Coulomb-nuclear interference (CNI) region at higher energies--much care is needed in extracting the numerical value of $rho$ for such energies. Thus, the true value of $rho$ would be higher than the TOTEM value for $rho$ found under the hypothesis that the real part of the elastic nuclear amplitude is devoid of such a zero in the CNI region.
rate research
Read More
We revisit a discussion on the impact-parameter dependence of proton-proton elastic scattering amplitude with improved uncertainty calculation. This analysis allows to reveal the asymptotic properties of hadron interactions. New data indicates that the impact-parameter elastic scattering amplitude is slightly above the black disk limit at 13~TeV c.m.s. energy of the LHC reaching a value of $mathrm{Im},H(s,0) = 0.512pm 0.001 text{(sys+stat)} pm 0.004 text{(norm)}$ confirming that black disk limit is violated at current collision energy, however it was not exceeded at 7~TeV. The growth trend of the impact-parameter amplitude imaginary part, extrapolated from previous and new data, indicates that it is unlikely that the amplitude is close to saturation. New analysis is consistent with smooth energy evolution of the elastic scattering amplitude and supersedes the earlier conclusion on the black disk limit excess observed at 7~TeV.
The recent data by the TOTEM Collaboration on $sigma_{tot}$ and $rho$ at 13 TeV, have shown agreement with a leading Odderon contribution at the highest energies, as demonstrated in the very recent analysis by Martynov and Nicolescu (MN). In order to investigate the same dataset by means of Pomeron dominance, we introduce a general class of forward scattering amplitude, with leading contributions even under crossing, associated with simple, double and triple poles in the complex angular momentum plane. For the lower energy region, we consider the usual non-degenerated Regge trajectories, with even and odd symmetry. The analytic connection between $sigma_{tot}$ and $rho$ is obtained by means of dispersion relations and we carry out fits to $pp$ and $bar{p}p$ data in the interval $sqrt{s}=5$ GeV - 13 TeV; following MN we consider only the TOTEM data at the LHC energy region. From the fits, we conclude that the general analytic model, as well as some particular cases representing standard parameterizations, are not able to describe satisfactorily the $sigma_{tot}$ and $rho$ data at 13 TeV. Further analyses in course and some perspectives are outlined.
We show that a Z with suppressed couplings to the electron compared to the Z-boson, with couplings to the b-quark, and with a mass close to the mass of the Z-boson, provides an excellent fit to forward-backward asymmetry of the b-quark and R_b measured on the Z-pole and $pm 2$ GeV off the Z-pole, and to A_e obtained from the measurement of left-right asymmetry for hadronic final states. It also leads to a significant improvement in the total hadronic cross section on the Z-pole and R_b measured at energies above the Z-pole. In addition, with a proper mass, it can explain the excess of $Zbbar b$ events at LEP in the 90-105 GeV region of the $bbar b$ invariant mass.
Recent data from LHC13 by the TOTEM Collaboration on $sigma_{tot}$ and $rho$ have indicated disagreement with all the Pomeron model predictions by the COMPETE Collaboration (2002). On the other hand, as recently demonstrated by Martynov and Nicolescu (MN), the new $sigma_{tot}$ datum and the unexpected decrease in the $rho$ value are well described by the maximal Odderon dominance at the highest energies. Here, we discuss the applicability of Pomeron dominance through fits to the textit{most complete set} of forward data from $pp$ and $bar{p}p$ scattering. We consider an analytic parametrization for $sigma_{tot}(s)$ consisting of non-degenerated Regge trajectories for even and odd amplitudes (as in the MN analysis) and two Pomeron components associated with double and triple poles in the complex angular momentum plane. The $rho$ parameter is analytically determined by means of dispersion relations. We carry out fits to $pp$ and $bar{p}p$ data on $sigma_{tot}$ and $rho$ in the interval 5 GeV - 13 TeV (as in the MN analysis). Two novel aspects of our analysis are: (1) the dataset comprises all the accelerator data below 7 TeV and we consider textit{three independent ensembles} by adding: either only the TOTEM data (as in the MN analysis), or only the ATLAS data, or both sets; (2) in the data reductions to each ensemble, uncertainty regions are evaluated through error propagation from the fit parameters, with 90 % CL. We argument that, within the uncertainties, this analytic model corresponding to soft Pomeron dominance, does not seem to be excluded by the textit{complete} set of experimental data presently available.
We present the new CTEQ-TEA global analysis of quantum chromodynamics (QCD). In this analysis, parton distribution functions (PDFs) of the nucleon are determined within the Hessian method at the next-to-next-to leading order (NNLO) in perturbative QCD, based on the most recent measurements from the Large Hadron Collider (LHC) and a variety of world collider data. Because of difficulties in fitting both the ATLAS 7 and 8 TeV $W$ and $Z$ vector boson production cross section data, we present two families of PDFs, named CT18 and CT18$Z$ PDFs, respectively, without and with the ATLAS 7 TeV $W$ and $Z$ measurements. We study the impact of the CT18 family of PDFs on the theoretical predictions of standard candle cross sections at the LHC.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
