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تسجيل مستخدم جديدFirst measurement of elastic, inelastic and total cross-section at $sqrt{s}=13$ TeV by TOTEM and overview of cross-section data at LHC energies
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The TOTEM collaboration has measured the proton-proton total cross section at $sqrt{s}=13$ TeV with a luminosity-independent method. Using dedicated $beta^{*}=90$ m beam optics, the Roman Pots were inserted very close to the beam. The inelastic scattering rate has been measured by the T1 and T2 telescopes during the same LHC fill. After applying the optical theorem the total proton-proton cross section is $sigma_{rm tot}=(110.6 pm 3.4$) mb, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections: $sigma_{rm el} = (31.0 pm 1.7)$ mb and $sigma_{rm inel} = (79.5 pm 1.8)$ mb.
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The TOTEM collaboration has measured the elastic proton-proton differential cross section ${rm d}sigma/{rm d}t$ at $sqrt{s}=13$ TeV LHC energy using dedicated $beta^{*}=90$ m beam optics. The Roman Pot detectors were inserted to 10$sigma$ distance fr
om the LHC beam, which allowed the measurement of the range $[0.04$ GeV$^{2}$$; 4 $GeV$^{2}$$]$ in four-momentum transfer squared $|t|$. The efficient data acquisition allowed to collect about 10$^{9}$ elastic events to precisely measure the differential cross-section including the diffractive minimum (dip), the subsequent maximum (bump) and the large-$|t|$ tail. The average nuclear slope has been found to be $B=(20.40 pm 0.002^{rm stat} pm 0.01^{rm syst})~$GeV$^{-2}$ in the $|t|$-range $0.04~$GeV$^{2}$ to $0.2~$GeV$^{2}$. The dip position is $|t_{rm dip}|=(0.47 pm 0.004^{rm stat} pm 0.01^{rm syst})~$GeV$^{2}$. The differential cross section ratio at the bump vs. at the dip $R=1.77pm0.01^{rm stat}$ has been measured with high precision. The series of TOTEM elastic pp measurements show that the dip is a permanent feature of the pp differential cross-section at the TeV scale.
Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at $sqrt{s} = 7 $ TeV in special runs with the Roman Pot detectors placed as close to the outgoing beam as seven times the transverse beam si
ze. The differential cross-section measurements are reported in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be (98.3 +- 0.2(stat) +- 2.8(syst)) mb.
The TOTEM experiment has made a precise measurement of the elastic proton-proton differential cross-section at the centre-of-mass energy sqrt(s) = 8 TeV based on a high-statistics data sample obtained with the beta* = 90 optics. Both the statistical
and systematic uncertainties remain below 1%, except for the t-independent contribution from the overall normalisation. This unprecedented precision allows to exclude a purely exponential differential cross-section in the range of four-momentum transfer squared 0.027 < |t| < 0.2 GeV^2 with a significance greater than 7 sigma. Two extended parametrisations, with quadratic and cubic polynomials in the exponent, are shown to be well compatible with the data. Using them for the differential cross-section extrapolation to t = 0, and further applying the optical theorem, yields total cross-section estimates of (101.5 +- 2.1) mb and (101.9 +- 2.1) mb, respectively, in agreement with previous TOTEM measurements.
TOTEM has measured the differential cross-section for elastic proton-proton scattering at the LHC energy of {srud}s = 7TeV analysing data from a short run with dedicated large {beta} * optics. A single exponential fit with a slope B = (20:1{pm}0:2sta
t {pm}0:3syst)GeV-2 describes the range of the four-momentum transfer squared |t| from 0.02 to 0.33 GeV2. After the extrapolation to |t| = 0, a total elastic scattering cross-section of (24:8{pm}0:2stat {pm}1:2syst) mb was obtained. Applying the optical theorem and using the luminosity measurement from CMS, a total proton-proton cross-section of (98:3{pm}0:2stat {pm}2:8syst) mb was deduced which is in good agreement with the expectation from the overall fit of previously measured data over a large range of center-of-mass energies. From the total and elastic pp cross-section measurements, an inelastic pp cross-section of (73:5{pm}0:6stat +1:8 -1:3 syst) mb was inferred. PACS 13.60.Hb: Total and inclusive cross sections
Using a data sample corresponding to an integrated luminosity of $2.0,fb^{-1}$, collected by the LHCb experiment, the production of the $eta_c(1S)$ state in proton-proton collisions at a centre-of-mass energy of $sqrt{s}=13 text{ TeV}$ is studied in
the rapidity range ${2.0 < y < 4.5}$ and in the transverse momentum range ${6.5 < p_{T} < 14.0text{ GeV}}$. The cross-section for prompt production of $eta_c(1S)$ mesons relative to that of the $J/psi$ meson is measured using the ${pbar{p}}$ decay mode and is found to be ${sigma_{eta_c(1S)}/sigma_{J/psi} = 1.69 pm 0.15 pm 0.10 pm 0.18}$. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the ${J/psito p bar{p}}$ and ${eta_cto p bar{p}}$ decays. The prompt $eta_c(1S)$ production cross-section is determined to be ${sigma_{eta_c(1S)} = 1.26 pm 0.11pm 0.08 pm 0.14 ,mu b}$, where the last uncertainty includes that on the ${J/psi}$ meson cross-section. The ratio of the branching fractions of $b$-hadron decays to the $eta_c(1S)$ and ${J/psi}$ states is measured to be ${mathcal{B}_{btoeta_c X}/mathcal{B}_{bto J/psi X} = 0.48 pm 0.03 pm 0.03 pm 0.05}$, where the last uncertainty is due to those on the branching fractions of the ${J/psi to p bar{p}}$ and ${eta_cto p bar{p}}$ decays. The difference between the ${J/psi}$ and $eta_c(1S)$ masses is also determined to be ${113.0 pm 0.7 pm 0.1text{ MeV}}$, which is the most precise single measurement of this quantity to date.
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