Measurement of Z-boson production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=8.16$ TeV and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity $-4 < \eta_{\mu} < -2.5$ and transverse momentum $p_{\rm T}^{\mu} > 20$ GeV/$c$ in the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite-sign dimuons with invariant mass $60 < m^{\mu\mu} < 120$ GeV$c^2$ and rapidity $2.5 < y_{cms}^{\mu\mu} < 4$. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward ($-4.46< y_{cms}^{\mu\mu}<-2.96$) and forward ($2.03< y_{cms}^{\mu\mu}<3.53$) rapidity regions. For the p-Pb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear-modified PDFs. For the Pb-Pb collisions, a $3.4\sigma$ deviation is seen in the integrated yield between the data and calculations based on the free-nucleon PDFs, while good agreement is found once nuclear modifications are considered.
Differential fiducial cross section in p-Pb
Integrated fiducial invariant yield in Pb-Pb
Rapidity differential fiducial invariant yield in Pb-Pb
Measurements of the proton structure function $F_2$ for $0.6 < Q^2 < 17 {GeV}^2$ and $1.2 \times 10^{-5} < x <1.9 \times 10^{-3}$ from ZEUS 1995 shifted vertex data are presented. From ZEUS $F_2$ data the slopes $dF_2/d\ln Q^2$ at fixed $x$ and $d\ln F_2/d\ln(1/x)$ for $x < 0.01$ at fixed $Q^2$ are derived. For the latter E665 data are also used. The transition region in $Q^2$ is explored using the simplest non-perturbative models and NLO QCD. The data at very low $Q^2$ $\leq 0.65 {GeV}^2$ are described successfully by a combination of generalised vector meson dominance and Regge theory. From a NLO QCD fit to ZEUS data the gluon density in the proton is extracted in the range $3\times 10^{-5} < x < 0.7$. Data from NMC and BCDMS constrain the fit at large $x$. Assuming the NLO QCD description to be valid down to $Q^2\sim 1 {GeV}^2$, it is found that the $q\bar{q}$ sea distribution is still rising at small $x$ and the lowest $Q^2$ values whereas the gluon distribution is strongly suppressed.
F2.
F2.
F2.
The reaction pp->d K+ Kbar0 has been investigated at an excess energy of Q=46 MeV above the (K+ Kbar0) threshold with ANKE at COSY-Juelich. From the detected coincident dK+ pairs about 1000 events with a missing Kbar0 were identified, corresponding to a total cross section of sigma(pp->d K+ Kbar0)=(38 +/- 2(stat) +/- 14(syst)) nb. Invariant-mass and angular distributions have been jointly analyzed and reveal s-wave dominance between the two kaons, accompanied by a p-wave between the deuteron and the kaon system. This is interpreted in terms of a0+(980)-resonance production.
Total cross section for P P --> DEUT K+ KBAR0.
Centre of mass angular distribution of the deuteron with respect to the direction of the incoming proton.
Centre of mass angular distribution of the vector joining the K+ and KBAR0 with respect to the direction of the incoming proton.
Antilambda production is studied inK−p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive\(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ(\(\bar \Lambda \)) increasing by a factor of four between 14.3 and 32 GeV/c. Thep⊥2 distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)−2. Most of the\(\bar \Lambda \)'s are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for\(\bar \Lambda \) production inK-p→Λ\(\bar \Lambda \)+XK-p→\(\bar \Lambda \)Kn+X, andK-p→\(\bar \Lambda \)p+X.
No description provided.
Antiproton-proton annihilations into final states containing one or two K10-mesons are studied on the basis of 450 000 pictures from the CERN 2 m HBC. The experiment covers the domain of antiproton incident momentum from 1.50 to 2.04 GeV/c. The resonance production rates are computed for the most abundant channels. The K10K10 threshold effect is explained through the inelastic channel π+π− → K10K10. The decay modes D, E → δ±(975)π∓, δ±(975) → K10K± are pointed out. The strange mesons C and C′ are observed in these annihilations and come mainly from the two-body channels \(p\bar p\) → (C, C′)K and\(p\bar p\) → (C, C′)K*.
RESONANCE FRACTIONS FOR AP P --> KS (K+ PI- + K- PI+).
RESONANCE FRACTIONS FOR AP P --> KS (K+ PI- + K- PI+) PI0.
RESONANCE FRACTIONS FOR AP P --> KS KS PI+ PI-.
The cross sections for the reaction p¯+p→K++K−+π++π− were measured at six momenta from 400 to 670 MeV/c. Various effective mass distributions indicate that about 37% of the reaction involves K*0 or K¯*0, 16% proceeds via the intermediate state K*0+K¯*0, about 21% involves ρ, 5% proceeds via the ϕ+ρ state, and the rest follows phase space.
No description provided.
Fraction obtained from the effective mass distribution.
Fraction obtained from the effective mass distribution.
The p p elastic differential cross section at 30 GeV/ c incident momentum has been measured in a two-arm spectrometer experiment (WA7) at the CERN SPS. The | t |-range covered extends from 0.5 to 5.8 (GeV/ c ) 2 . A pronounced dip-bump structure is observed, with a sharp minimum around | t | ≈ 1.7 (GeV/ c ) 2 . The results are compared with existing p p data at lower energies and with our earlier p p data at 50 GeV/ c . A number of model predictions are discussed. We also compare the p p 30 GeV/ c differential cross section with that of pp at the same momentum. Finally, the energy dependence of the p p fixed-| t | differential cross in the incident momentum range 3.6 to 50 GeV/ c is presented.
NUMERICAL VALUES SUPPLIED BY D. IMRIE. ERROR CONTAINS BOTH STATISTICS AND SYSTEMATICS.
The p̄p total annihilation cross section has been measured, with the Obelix apparatus at LEAR, at ten values of the antiproton incident momentum between 43 and 175 MeV/ c . The values of the cross section show that the well known 1 p behaviour of the annihilation cross section is drastically modified at very low momenta, which demonstrates the important role of the Coulomb force in low energy p̄p interaction. Moreover, they do not present any explicit resonant behaviour. Finally, when compared to potential model calculations, the data suggest that the percentage of P-wave in p̄p interaction around 50 MeV/ c antiproton incident momentum is less than 5%.
No description provided.
None
No description provided.
Differential cross sections for the reaction gamma p -> eta-prime p have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results reported here possess much greater accuracy than previous measurements. Analyses of these data indicate for the first time the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710) resonances, known to couple strongly to the eta N channel in photoproduction on the proton, and the importance of j=3/2 resonances in the process.
Differential cross sections for ETAPRIME photoproduction on the proton at photon energies 1.527, 1.577 and 1.627 GeV. The errors shown are combined statistical and systematic.
Differential cross sections for ETAPRIME photoproduction on the proton at photon energies 1.677, 1.728 and 1.779 GeV. The errors shown are combined statistical and systematic.
Differential cross sections for ETAPRIME photoproduction on the proton at photon energies 1.829, 1.879 and 1.930 GeV. The errors shown are combined statistical and systematic.
Forum