119257623
An updated analysis on the rise of the hadronic total cross-section at the LHC energy region
pp elastic scattering above 5 GeV is presented. The dataset includes the recent high-precision TOTEM measurements of the pp total and elastic (integrated) cross-sections at 7 TeV and 8 TeV. Following previous works, the leading high-energy contribution for the total cross-section (�tot) is parametrized as ln(s/sh), where and sh are free real fit parameters. Singly-subtracted derivative dispersion relations are used to connecttot and the rho parameter (�) in an analytical way. Different fit procedures are considered, including individual fits totot data, global fits totot anddata, constrained and unconstrained data reductions. The results favor a rise of thetot faster than the log-squared bound by Froissart and Martin at the LHC energy region. The parametrization fortot is extended to fit the elastic cross-section (�el) data with satisfactory results. The analysis indicates an asymptotic ratioel/�tot consistent with 1/3 (as already obtained in a previous work). A critical discussion on the correlation, practical role and physical implications of the parameters and sh is presented. The discussion confronts the 2002 prediction oftot by the COMPETE Collaboration and the recent result by the Particle Data Group (2012 edition of the Review of Particle Physics). Some conjectures on possible implications of a fast rise of the proton-proton total cross-section at the highest energies are also presented.
118693161
On the rise of proton-proton cross-sections at high energies
The rise of total, elastic and inelastic hadronic cross sections at high energies is investigated by means of an analytical parametrization, with the exponent of the leading logarithm contribution as a free fit parameter. Using derivative dispersion relations with one subtraction, two different fits to proton–proton and antiproton–proton total cross section and ρ parameter data are developed, reproducing well the experimental information in the energy region 5 GeV–7 TeV. The parametrization for the total cross sections is then extended to fit the elastic (integrated) cross section data in the same energy region, with satisfactory results. From these empirical results we extract the energy dependence of several physical quantities: inelastic cross section, ratios elastic/total, inelastic/total cross sections, ratio total-cross-section/elastic-slope, elastic slope and optical point. All data, fitted and predicted, are quite well described. We find a statistically consistent solution indicating: (1) an increase of the hadronic cross sections with the energy faster than the log-squared bound by Froissart and Martin; (2) asymptotic limits 1/3 and 2/3 for the ratios elastic/total and inelastic/total cross sections, respectively; a result in agreement with unitarity. These indications corroborate recent theoretical arguments by Azimov on the rise of the total cross section.
118623530
Total Hadronic Cross-Section Data and the Froissart–Martin Bound
The energy dependence of the total hadronic cross section at high energies is investigated with focus on the recent experimental result by the Total Elastic and Diffractive Cross-section Measurement Collaboration at 7 TeV and the Froissart–Martin bound. On the basis of a class of analytical parametrization with the exponent γ in the leading logarithm contribution as a free parameter, different variants of fits to pp and $\bar{\textrm{p}}$p total cross-section data above 5 GeV are developed. Two ensembles are considered, the first comprising data up to 1.8 TeV and the second also including the data collected at 7 TeV. We show that in all fit variants applied to the first ensemble, the exponent is statistically consistent with γ = 2. Applied to the second ensemble, however, the same variants yield γ values above 2, a result already obtained in two other analysis, by Amaldi et al. and by the UA4/2 Collaboration. As recently discussed by Azimov, this faster-than-squared-logarithm rise does not necessarily violate unitarity. Our results suggest that the energy dependence of the hadronic total cross section at high energies still constitutes an open problem.
119217774
Reply to 'Commentary on 'Total Hadronic Cross Section Data and the Froissart-Martin Bound', by Fagundes, Menon and Silva'
A reply to the above mentioned commentary by M.M. Block and F. Halzen on our quoted work is presented. We answer to each point raised by these authors and argument that our data reductions, strategies and methodology are adequate to the nonlinear-fit-problem in focus. In order to exemplify some arguments, additional information from our subsequent analysis is referred to. A brief commentary on the recent results by Block and Halzen is also presented. We understand that this reply gives support to the results and conclusions presented in our quoted work.
119280988
Preliminary results on the empirical applicability of the Tsallis distribution in elastic hadron scattering
We show that the proton-proton elastic differential cross section data at dip position and beyond can be quite well described by a parametrization based on the Tsallis distribution, with only five free fit parameters. Extrapolation of the results obtained at 7 TeV to large momentum transfer, suggests that hadrons may not behave as a black-disk at the asymptotic energy region.
118857116
Recent results on Top quark Physics with the ATLAS and CMS experiments
An overview of the most recent results on top quark physics obtained using proton-proton collision data collected with the ATLAS and the CMS experiments at 7 TeV center-of-mass energy is given. Measurements for inclusive and differential top quark pair or single top quark production in different final states are reviewed. Top properties such as W helicity in top decays, electric charge, charge asymmetry and spin correlations of top quark pairs, among others have also been measured by the LHC experiments. All the measurements are found to be consistent with the Standard Model predictions with a good level of accuracy. The latest results in the measurement of the top quark mass at the LHC are also presented and discussed.
117483857
Search for quark contact interactions in dijet angular distributions in pp collisions at s=7 TeV measured with the ATLAS detector
Dijet angular distributions from the first LHC pp collisions at center-of-mass energy sqrt(s) = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb-1. Dijet $\chi$ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the $\chi$ distributions excludes quark contact interactions with a compositeness scale $\Lambda$ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.
66116773
A mobile data acquisition system
A mobile data aquisition (MobiDAQ) was developed for the ATLAS central hadronic calorimeter (TileCal). MobiDAQ has been designed in order to test the functionalities of the TileCal front-end electronics and to acquire calibration data before the final back-end electronics were built and tested. MobiDAQ was also used to record the first cosmic ray events acquired by an ATLAS subdetector in the underground experimental area.
18513841
Fitting BOOMERANG and MAXIMA-1 data with a Einstein–Yang–Mills cosmological model
Abstract We analyse the implications of recent Cosmic Microwave Background (CMB) data for a specific cosmological model, based on the higher-dimensional Einstein–Yang–Mills system compactified on a R × S 3 × S d topology and conclude that the model parameters are tightly constrained by CMB spectra. Moreover, the model predicts a relationship between the deceleration parameter at present, q 0 , and some characteristic features of CMB spectra, namely, the height of the first peak and the the location of the second peak, that is consistent with the observations and which can be further tested by future CMB and other experiments.
118795909
Singlet Majorana fermion dark matter, DAMA, CoGeNT, and CDMS-II
We propose a model where a sterile Majorana fermion with mass in the range of 10 GeV-1 TeV can account for the whole amount of dark matter in the Universe. The model involves a right-handed singlet Majorana fermion as a weakly interacting massive particle, a charged and a neutral scalar, and all singlets by the standard model symmetry and makes use of a discrete symmetry in order to guarantee the singlet fermion stability. Also, motivated by the recent results reported by CoGeNT and CDMS-II experiments concerning excess events of the expected background, and the intriguing annual modulation observed by DAMA, we look for a possible explanation to some of these experiments. Our results show that there is a lot of room in the parameter space to make this sterile Majorana fermion a viable dark matter candidate, and, if it is realized in nature, it is also capable of explaining DAMA annual modulation signal and/or CoGeNT excess events or CDMS-II excess event candidates. Besides, a light Higgs boson is preferred in this scenario.