Differential cross sections for the Drell-Yan process, including Z boson production, using the dimuon decay channel are measured in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of 8.16 TeV. A data sample recorded with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 173 nb$^{-1}$. The differential cross section as a function of the dimuon mass is measured in the range 15-600 GeV, for the first time in proton-nucleus collisions. It is also reported as a function of dimuon rapidity over the mass ranges 15-60 GeV and 60-120 GeV, and ratios for the p-going over the Pb-going beam directions are built. In both mass ranges, the differential cross sections as functions of the dimuon transverse momentum $p_\mathrm{T}$ and of a geometric variable $\phi^*$ are measured, where $\phi^*$ highly correlates with $p_\mathrm{T}$ but is determined with higher precision. In the Z mass region, the rapidity dependence of the data indicate a modification of the distribution of partons within a lead nucleus as compared to the proton case. The data are more precise than predictions based upon current models of parton distributions.
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of dimuon invariant mass. The quoted error is the quadratic sum of the statistical and systematic uncertainties. The global normalisation uncertainty of 3.5% is listed separately.
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of rapidity in the centre-of-mass frame for $15<m_{\mu\mu}<60$ GeV. The quoted error is the quadratic sum of the statistical and systematic uncertainties. The global normalisation uncertainty of 3.5% is listed separately.
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of rapidity in the centre-of-mass frame for $60<m_{\mu\mu}<120$ GeV. The quoted error is the quadratic sum of the statistical and systematic uncertainties. The global normalisation uncertainty of 3.5% is listed separately.
The inclusive production rates of isolated, prompt photons in $p$+Pb collisions at $\sqrt{s_\mathrm{NN}} = 8.16$ TeV are studied with the ATLAS detector at the Large Hadron Collider using a dataset with an integrated luminosity of 165 nb$^{-1}$ recorded in 2016. The cross-section and nuclear modification factor $R_{p\mathrm{Pb}}$ are measured as a function of photon transverse energy from 20 GeV to 550 GeV and in three nucleon-nucleon centre-of-mass pseudorapidity regions, (-2.83,-2.02), (-1.84,0.91), and (1.09,1.90). The cross-section and $R_{p\mathrm{Pb}}$ values are compared with the results of a next-to-leading-order perturbative QCD calculation, with and without nuclear parton distribution function modifications, and with expectations based on a model of the energy loss of partons prior to the hard scattering. The data disfavour a large amount of energy loss and provide new constraints on the parton densities in nuclei.
The measured cross sections for prompt, isolated photons with rapidity in (1.09,1.90).
The measured cross sections for prompt, isolated photons with rapidity in (−1.84,0.91).
The measured cross sections for prompt, isolated photons with rapidity in (−2.83,−2.02).
We report on the measurement of $\rm{J}/\psi$ production in the dielectron channel at mid-rapidity (|y|<1) in p+p and d+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider. The transverse momentum $p_{T}$ spectra in p+p for $p_{T}$ < 4 GeV/c and d+Au collisions for $p_{T}$ < 3 GeV/c are presented. These measurements extend the STAR coverage for $\rm{J}/\psi$ production in p+p collisions to low $p_{T}$. The $<p_{T}^{2}>$ from the measured $\rm{J}/\psi$ invariant cross section in p+p and d+Au collisions are evaluated and compared to similar measurements at other collision energies. The nuclear modification factor for $\rm{J}/\psi$ is extracted as a function of $p_{T}$ and collision centrality in d+Au and compared to model calculations using the modified nuclear Parton Distribution Function and a final-state $\rm{J}/\psi$ nuclear absorption cross section.
The mean square of $p_T$.
Nuclear absorption cross section.
The nuclear modicifation factor vs. $p_T$ for $J\psi$ with |y| < 1 in 0-100 percent central d+Au collisions.
The results of measured inclusive double differential cross section of α particles emitted in the interaction of 12C ions with 59Co and 93Nb at incident energies of 300 and 400 MeV are presented. The analysis of these data allows us to isolate the contributions of the different reaction mechanisms, thereby confirming previous conclusions of a comprehensive analysis of a large number of excitation function, forward recoil ranges and angular distributions of residues produced in the interaction of 12C with a target nucleus in the same mass range. In particular, the probabilities associated with α-particle reemission following incomplete fussion processes have been reaffirmed. Several refinements to the theoretical model proposed in earlier studies of the interaction of 12C with nuclei are presented.
No description provided.
Reaction cross sections and production cross sections for neutrons, hydrogen, and helium have been measured for 1.2, 1.8 GeV p+Fe, Ni, Ag, Ta, W, Au, Pb and U and are compared with different intra-nuclear-cascade- combined with evaporation-models. Agreement for neutrons and considerable differences for light charged particles are observed between experiment and calculation as well as between different models. The discrepancies are associated with specific deficiencies in the models. The exclusive data measured with two 4π-detectors for neutron and charged particle detection allowed furthermore a systematic comparison of observables characteristic of different stages of the temporal evolution of a spallation reaction: inelastic collision probability, excitation energy distribution, pre-equilibrium emission, and inclusive production cross sections.
No description provided.
No description provided.
No description provided.
Reactions of a 41 MeV/u beam of the radioactive halo nucleus 11Be have been studied with a counter telescope coupled to an array of neutron detectors covering angles up to 97°. The technique allows to determine single-neutron inclusive and exclusive angular distributions. The targets (Be, Ti and Au) were chosen to illustrate the relative roles played by nuclear and Coulomb mechanisms. The channels leading to 10Be, the dissociation channels, correspond to impact parameters larger than the sum of the radii of the target and the 10Be core. It is shown that for the dissociation process it is possible to account almost quantitatively for the integral, single- and double-differential cross sections from models without free parameters including the Coulomb, Serber and Glauber (diffraction-dissociation) mechanisms. The neutron distributions from the nondissociative reaction channels show little individuality and it is convenient to group them together as the channel “neutron plus anything different from 10Be”. We refer to these as “restricted-inclusive” reactions. These seem to be a promising tool for obtaining accurate information on the halo wave function in momentum coordinates.
INTEGRAL SIGMA(BE10) FOLLOWING PROJECTILE BREAKUP.
No description provided.
IN THE REACTION X IS NOT BE10.
Neutrons arising from the breakup of a 30 MeV/nucleon 19 C beam on a tantalum target have been measured using the 98 element array DEMON. A narrow, forward peaked neutron angular distribution, with a corresponding momentum spread considerably smaller than those measured simultaneously for 21 N, 22 O and 24 F, was observed for charged fragments with Z < Z proj . Interpreted in terms of the core-breakup reaction model, the results support the existence of a one neutron halo in 19 C.
No description provided.
No description provided.
At the projectile-fragment separator FRS of GSI, relativistic secondary beams of about 520 MeV/nucleon were produced by fragmentation of a primary beam of58Ni at 650 MeV/nucleon in a beryllium target. By means of aΔE—Bρ—TOF measurement, the fragments have been identified and their charge-changing probabilities in targets of CH2, C, Al, and Pb have been determined. We describe the results for the total charge-changing cross sections in this first paper, whereas a second article deals with the partial charge-changing cross sections. At the drip line, the measured charge-changing cross sections exhaust close to 100% of the total interaction cross sections as calculated with semiempirical models. The measurements at the proton drip line with low-Z targets indicate that only a very small increase of the cross sections may be observed, whereas the measurements with a lead target show that no significant increase of the total charge-changing cross sections is present which would be a hint for low-lying dipole strength. Our experimental data are compared to Glauber-type calculations.
Nucleus is C H2.
Nucleus is C H2.
Nucleus is C H2.
The projectile fission of uranium at relativistic energy impinging on a Be target was investigated with the fragment separator, FRS, in order to produce and identify new isotopes and to measure their production yields. Fifty eight new fragments have been observed with a neutron excess of (N - Z)/Z reaching 0.8 and cross sections as small as 0.3 nb.
No description provided.
The combined cross section for absorption and charge exchange interactions of positively charged pions with carbon nuclei for the momentum range 200 MeV/c to 300 MeV/c have been measured with the DUET experiment at TRIUMF. The uncertainty is reduced by nearly half compared to previous experiments. This result will be a valuable input to existing models to constrain pion interactions with nuclei.
Summary of the measurements. In this table, $p_\pi$ is the momentum of pions at the fiber tracker.
Forum