No Arabic abstract
In this paper, we report the measurement relative to the production of forward neutrons in proton-proton collisions at $mathrm{sqrt{s} = 13~TeV}$ obtained using the LHCf Arm2 detector at the Large Hadron Collider. The results for the inclusive differential production cross section are presented as a function of energy in three different pseudorapidity regions: $eta > 10.76$, $8.99 < eta < 9.22$ and $8.81 < eta < 8.99$. The analysis was performed using a data set acquired in June 2015 that corresponds to an integrated luminosity of $mathrm{0.194~nb^{-1}}$. The measurements were compared with the predictions of several hadronic interaction models used to simulate air showers generated by Ultra High Energy Cosmic Rays. None of these generators showed good agreement with the data for all pseudorapidity intervals. For $eta > 10.76$, no model is able to reproduce the observed peak structure at around $mathrm{5~TeV}$ and all models underestimate the total production cross section: among them, QGSJET II-04 shows the smallest deficit with respect to data for the whole energy range. For $8.99 < eta < 9.22$ and $8.81 < eta < 8.99$, the models having the best overall agreement with data are SIBYLL 2.3 and EPOS-LHC, respectively: in particular, in both regions SIBYLL 2.3 is able to reproduce the observed peak structure at around $mathrm{1.5-2.5~TeV}$.
In this paper, we report the production cross-section of forward photons in the pseudorapidity regions of $eta,>,10.94$ and $8.99,>,eta,>,8.81$, measured by the LHCf experiment with proton--proton collisions at $sqrt{s}$ = 13 TeV. The results from the analysis of 0.191 $mathrm{nb^{-1}}$ of data obtained in June 2015 are compared to the predictions of several hadronic interaction models that are used in air-shower simulations for ultra-high-energy cosmic rays. Although none of the models agree perfectly with the data, EPOS-LHC shows the best agreement with the experimental data among the models.
In this paper, we report the measurement of the energy flow, the cross section and the average inelasticity of forward neutrons (+ antineutrons) produced in $sqrt{s} = 13$ TeV proton-proton collisions. These quantities are obtained from the inclusive differential production cross section, measured using the LHCf Arm2 detector at the CERN Large Hadron Collider. The measurements are performed in six pseudorapidity regions: three of them ($eta > 10.75$, $8.99 < eta < 9.21$ and $8.80 < eta < 8.99$), albeit with smaller acceptance and larger uncertainties, were already published in a previous work, whereas the remaining three ($10.06 < eta < 10.75$, $9.65 < eta < 10.06$ and $8.65 < eta < 8.80$) are presented here for the first time. The analysis was carried out using a data set acquired in June 2015 with a corresponding integrated luminosity of $mathrm{0.194~nb^{-1}}$. Comparing the experimental measurements with the expectations of several hadronic interaction models used to simulate cosmic ray air showers, none of these generators resulted to have a satisfactory agreement in all the phase space selected for the analysis. The inclusive differential production cross section for $eta > 10.75$ is not reproduced by any model, whereas the results still indicate a significant but less serious deviation at lower pseudorapidities. Depending on the pseudorapidity region, the generators showing the best overall agreement with data are either SIBYLL 2.3 or EPOS-LHC. Furthermore, apart from the most forward region, the derived energy flow and cross section distributions are best reproduced by EPOS-LHC. Finally, even if none of the models describe the elasticity distribution in a satisfactory way, the extracted average inelasticity is consistent with the QGSJET II-04 value, while most of the other generators give values that lie just outside the experimental uncertainties.
A measurement of the production cross-section of Z bosons in pp collisions at $sqrt{s} = 13$ TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range $2.0 < eta < 4.5$, transverse momenta $p_text{T} > 20$ GeV and dilepton invariant mass in the range $60<m(ellell)<120$ GeV. The integrated cross-section from averaging the two final states is begin{equation*}sigma_{text{Z}}^{ellell} = 194.3 pm 0.9 pm 3.3 pm 7.6text{ pb,}end{equation*} where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable $phi^*_eta$.
The production cross-section of $J/psi$ pairs is measured using a data sample of $pp$ collisions collected by the LHCb experiment at a centre-of-mass energy of $sqrt{s} = 13 ,{mathrm{TeV}}$, corresponding to an integrated luminosity of $279 pm 11 ,{mathrm{pb^{-1}}}$. The measurement is performed for $J/psi$ mesons with a transverse momentum of less than $10 ,{mathrm{GeV}}/c$ in the rapidity range $2.0<y<4.5$. The production cross-section is measured to be $15.2 pm 1.0 pm 0.9 ,{mathrm{nb}}$. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the $J/psi$ pair are measured and compared to theoretical predictions.