4He-p collisions at two values of4He momenta 8.6 GeV/c and 13.6 GeV/c as well as the3He-p collisions at 13.5 GeV/c have been studies using the one-meter JINR hydrogen bubble chamber. Total, elastic, topological and reaction cross sections have been measured. The cross sections have been determined on a sample of minimum biased events.
No description provided.
No description provided.
No description provided.
The exclusive electroproduction of J/psi mesons, ep->epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15<Q^2<0.8 GeV^2 and 2<Q^2<100 GeV^2 using integrated luminosities of 69 pb^-1 and 83 pb^-1, respectively.The photon-proton centre-of-mass energy was in the range 30<W<220 GeV and the squared four-momentum transfer at the proton vertex |t|<1.The cross sections and decay angular distributions are presented as functions of Q^2, W and t. The effective parameters of the Pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma_L/sigma_T, grows with Q^2, whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 0.15 to 0.18 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 2 to 5 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 5 to 10 GeV**2.
TheA-dependence of the polarization ofΛ0,s produced inclusively in neutron-nucleus interactions at a mean neutron momentum of about 40 GeV/c has been measured in an experiment performed using the BIS-2 spectrometer at the Serpukhov accelerator. Carbon, Aluminium and Copper targets were used. TheΛ0,s were produced in the kinematical region of 0.6<pT<1.3 GeV/c and 0.2<xF<0.9. Describing the polarization of theΛ0,s by ℘=a·A a value of (−0.15+0.07/−0.60) was obtained by a fit to our data.
POLARIZATION IS DESCRIBED BY A POWER LOW: POL = C*A**B, WHERE C = -1.1, +0.4, -0.3 , A- ATOMIC NUMBER AND B = -0.15, +0.07, -0.6.
.
Measurements of the kinematic distributions of $J/\psi$ mesons produced in $p-$C, $p-$Ti and $p-$W collisions at $\sqrt{s}=41.6 \mathrm{GeV}$ in the Feynman-$x$ region $-0.34 < x_{F} < 0.14$ and for transverse momentum up to $p_T = 5.4 \mathrm{GeV}/c$ are presented. The $x_F$ and $p_T$ dependencies of the nuclear suppression parameter, $\alpha$, are also given. The results are based on $2.4 \cdot 10^{5}$ $J/\psi$ mesons in both the $e^+ e^-$ and $\mu^{+}\mu^{-}$ decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of $x_{F}$ for the first time. The average value of $\alpha$ in the measured $x_{F}$ region is $0.981 \pm 0.015$. The data suggest that the strong nuclear suppression of $J/\psi$ production previously observed at high $x_F$ turns into an enhancement at negative $x_F$.
J/PSI distributions (dN/dp_T, normalized to their integrals over the measured range) for three targets materials with statistical and systematics uncertainties.
J/PSI distributions (dN/dx_F, normalized to their integrals over the measured range) for three targets materials with statistical and systematics uncertainties.
The parameter Alpha as a function of p_T. Statistical and systematic uncertainties are indicated separately.
The PHENIX experiment has measured mid-rapidity transverse momentum spectra (0.4 < p_T < 4.0 GeV/c) of single electrons as a function of centrality in Au+Au collisions at sqrt(s_NN) = 200 GeV. Contributions to the raw spectra from photon conversions and Dalitz decays of light neutral mesons are measured by introducing a thin (1.7% X_0) converter into the PHENIX acceptance and are statistically removed. The subtracted ``non-photonic'' electron spectra are primarily due to the semi-leptonic decays of hadrons containing heavy quarks (charm and bottom). For all centralities, charm production is found to scale with the nuclear overlap function, T_AA. For minimum-bias collisions the charm cross section per binary collision is N_cc^bar/T_AA = 622 +/- 57 (stat.) +/- 160 (sys.) microbarns.
Value of the Alpha power as used in a fit of dN/dy versus Ncoll of the form A*Ncoll^Alpha, where N is the non photonic electron yield and Ncoll the number of p+p collisions This value only includes data from Au+Au collisions The value of Alpha = 1 is the expectation in the absence of medium effects.
Value of the Alpha power as used in a fit of dN/dy versus Ncoll, of the form A*Ncoll^Alpha, where N is the non photonic electron yield and Ncoll the number of p+p collisions This value is calculated including previous data of p+p collisions, measured by PHENIX, in addition of the Au+Au data The value of Alpha = 1 is the expectation in the absence of medium effects.
Spectrum in transverse momentum of electrons created in open heavy flavor decays, for minimum bias events.
J/psi production in d+Au and p+p collisions at sqrt(s_NN) = 200 GeV has been measured by the PHENIX experiment at rapidities -2.2 < y < +2.4. The cross sections and nuclear dependence of J/\psi production versus rapidity, transverse momentum, and centrality are obtained and compared to lower energy p+A results and to theoretical models. The observed nuclear dependence in d+Au collisions is found to be modest, suggesting that the absorption in the final state is weak and the shadowing of the gluon distributions is small and consistent with Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-based parameterizations that fit deep-inelastic scattering and Drell-Yan data at lower energies.
J/PSI differential cross section in P+P reactions( times di-lepton branching ratio B=5.9%) as a function of rapidity.
J/PSI nuclear modification factor RDA,as a function of rapidity.
Total cross-section for J/PSI production in P P reactions. The total cross section is estimated using a pythia calculation, normalized to our data. The di-lepton branching ratio used is 5.9%.The systematic error given is due to the fit. The choice of the PDF and model was estimated to have little impact in the value of the total cross section.
The energy dependence of the photon-proton total cross section, sigma-tot, was determined from ep scattering data collected with the ZEUS detector at HERA at three values of the center-of-mass energy, W, of the gamma-p system in the range 194<W<296 GeV. This is the first determination of the W dependence of sigma-tot from a single experiment at high W. Parameterizing sigma-tot proportional to W^(2 epsilon), epsilon = 0.111 +/- 0.009 (stat.) +/- 0.036 (syst.) was obtained.
Ratios of the cross sections for 3 energy bins. The first DSYS error isthe uncorrelated uncertainty and the second is the correlated uncertainty.
Fitted power law energy dependence.
The STAR collaboration at RHIC presents measurements of \Jpsi$\to{e^+e^-}$ at mid-rapidity and high transverse momentum ($p_T>5$ GeV/$c$) in \pp and central \cucu collisions at \sNN = 200 GeV. The inclusive \Jpsi production cross section for \cucu collisions is found to be consistent at high $p_T$ with the binary collision-scaled cross section for \pp collisions, in contrast to previous measurements at lower $p_T$, where a suppression of \Jpsi production is observed relative to the expectation from binary scaling. Azimuthal correlations of $J/\psi$ with charged hadrons in \pp collisions provide an estimate of the contribution of $B$-meson decays to \Jpsi production of $13% \pm 5%$.
J/psi differential production cross section in sqrt(s).
J/psi transverse momentum distribution in sqrt(s).
J/psi transverse momentum distribution in sqrt(s).
A measurement of elastic deeply virtual Compton scattering gamma* p -> gamma p using e^+ p and e^- p collision data recorded with the H1 detector at HERA is presented. The analysed data sample corresponds to an integrated luminosity of 306 pb^-1, almost equally shared between both beam charges. The cross section is measured as a function of the virtuality Q^2 of the exchanged photon and the centre-of-mass energy W of the gamma* p system in the kinematic domain 6.5 < Q^2 < 80 GeV^2, 30 < W < 140 GeV and |t| < 1 GeV^2, where t denotes the squared momentum transfer at the proton vertex. The cross section is determined differentially in t for different Q^2 and W values and exponential t-slope parameters are derived. Using e^+ p and e^- p data samples, a beam charge asymmetry is extracted for the first time in the low Bjorken x kinematic domain. The observed asymmetry is attributed to the interference between Bethe-Heitler and deeply virtual Compton scattering processes. Experimental results are discussed in the context of two different models, one based on generalised parton distributions and one based on the dipole approach.
The DVCS cross section as a function of Q**2.
The DVCS cross section as a function of W.
The DVCS cross section as a function of W for three different Q**2 regions.
Exclusive rho^0 electroproduction at HERA has been studied with the ZEUS detector using 120 pb^{-1} of integrated luminosity collected during 1996-2000. The analysis was carried out in the kinematic range of photon virtuality 2 < Q^2 < 160 GeV$^2, and gamma^* p centre-of-mass energy 32 < W < 180 GeV. The results include the Q^2 and W dependence of the gamma^* p --> rho^0 p cross section and the distribution of the squared-four-momentum transfer to the proton. The helicity analysis of the decay-matrix elements of the rho^0 was used to study the ratio of the gamma^* p cross section for longitudinal and transverse photon as a function of Q^2 and W. Finally, an effective Pomeron trajectory was extracted. The results are compared to various theoretical predictions.
Measurement of the spin density matrix element r_04_00 as a function of Q**2.
Measurement of the spin density matrix element RE(r_04_10) as a function of Q**2.
Measurement of the spin density matrix element r_04_1-1 as a function of Q**2.
The yields of the 1S and the sum of the 2S and 3S Υ resonances have been measured for 800-GeV protons incident on targets of H2, C, Ca, Fe, and W. A significant nuclear dependence is seen in the yield per nucleon which, within errors, is the same for the Υ(1S) and Υ(2S+3D) states. A large decrease in the relative yield from heavy nuclei is found for the range xF<0. Significant nuclear dependence is also observed in the pt distribution. Differential cross sections for the Υ(1S) for H2 are presented over the ranges 0.24≤pt≤3.4 GeV/c and -0.15≤xF≤0.5.
Mass dependence as a function of feynman X for UPSI(1S) production.
Mass dependence as a function of feynman X for UPSI(2S/3S) production.
Mass dependence as a function of transverse momentum for UPSI(1S) production.
The inclusive production cross sections of the strange vector mesons K*0, K*0bar, and phi have been measured in interactions of 920 GeV protons with C, Ti, and W targets with the HERA-B detector at the HERA storage ring. Differential cross sections as a function of rapidity and transverse momentum have been measured in the central rapidity region and for transverse momenta up to pT=3.5 GeV/c. The atomic number dependence is parametrised as sigma(pA) = sigma(pN)*A**alpha, where sigma(pN) is the proton-nucleon cross section. Within the phase space accessible, alpha(K*0) = 0.86+/-0.03, alpha(K*0bar) = 0.87+/-0.03, and alpha(phi) = 0.96+/-0.02. The total proton-nucleon cross sections, determined by extrapolating the differential measurements to full phase space, are sigma(pN->K*0) = 5.06+/-0.54 mb, sigma(pN->K*0bar) = 4.02+/-0.45 mb, and sigma(pN->phi) = 1.17+/-0.11 mb. The Cronin effect is observed for the first time for vector mesons containing strange quarks/ compared to the measurements of Cronin et al. for K+- mesons, the measured values of alpha for phi mesons coincide with those of K- mesons for all transverse momenta, while the enhancement for K*0 / K*0bar mesons is smaller.
Measured rapidity distribution for K*0 production in the accessible phase space.
Measured rapidity distribution for K*BAR0 production in the accessible phase space.
Measured rapidity distribution for PHI production in the accessible phase space.
Cross sections for elastic production of J/Psi mesons in photoproduction and electroproduction are measured in electron proton collisions at HERA using an integrated luminosity of 55 pb^{-1}. Results are presented for photon virtualities Q^2 up to 80 GeV^2. The dependence on the photon-proton centre of mass energy W_{gamma p} is analysed in the range 40 < \Wgp < 305 GeV in photoproduction and 40 < \Wgp < 160 GeV in electroproduction. The \Wgp dependences of the cross sections do not change significantly with Q^2 and can be described by models based on perturbative QCD. Within such models, the data show a high sensitivity to the gluon density of the proton in the domain of low Bjorken x and low Q^2. Differential cross sections d\sigma/dt, where t is the squared four-momentum transfer at the proton vertex, are measured in the range |t|<1.2 GeV^2 as functions of \Wgp and Q^2. Effective Pomeron trajectories are determined for photoproduction and electroproduction. The J/Psi production and decay angular distributions are consistent with s-channel helicity conservation. The ratio of the cross sections for longitudinally and transversely polarised photons is measured as a function of Q^2 and is found to be described by perturbative QCD based models.
Cross section for elastic J/PSI photoproduction in Q**2 bins for W = 90 GeV and ABS(T) < 1.2 GeV**2.
Cross section for elastic J/PSI photoproduction in W bins for ABS(T) < 1.2 GeV**2 and Q**2 < 1 GeV**2.. There are two cross sections for the 205 to 235 GeV bin due to overlapping data sets. The mean is 151 +- 8 (DSYS=20) nb.
Cross section for elastic J/PSI photoproduction as a function of W in Q**2 bins for ABS(T) < 1.2 GeV**2.
Exclusive electroproduction of $\phi$ mesons has been studied in $e^\pm p$ collisions at $\sqrt{s}=318 \gev$ with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb$^{-1}$. The $\gamma^*p$ cross section is presented in the kinematic range $2<Q^2<70 \gev^2$, $35<W<145 \gev$ and ${|t|}<0.6 \gev^2$. The cross sections as functions of $Q^2$, $W$, $t$ and helicity angle $\theta_h$ are compared to cross sections for other vector mesons. The ratios $R$ of the cross sections for longitudinally and transversely polarized virtual photons are presented as functions of $Q^2$ and $W$. The data are also compared to predictions from theoretical models.
Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 2 to 3 GeV**2.
Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 3 to 5 GeV**2.
Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 5 to 9 GeV**2.
We have studied the diffractive dissociation into di-jets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where t_{min} approaches 0) we find that when the per-nucleus cross-section for this process is parameterized as $ \sigma = \sigma_0 A^{\alpha} $, $ \alpha $ has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.
Cross sections is fitted to A**POWER.
The diffractive photoproduction of J/psi mesons is measured with the H1 detector at the ep collider HERA using an integrated luminosity of 78 pb^-1. The differential cross section d sigma(gamma p -> J/psi Y) / d t is studied in the range 2 < |t| < 30 GeV^2, where t is the square of the four-momentum transferred at the proton vertex. The cross section is also presented as a function of the photon-proton centre-of-mass energy W in three t intervals, spanning the range 50 < W < 200 GeV. A fast rise of the cross section with W is observed for each t range and the slope for the effective linear Pomeron trajectory is measured to be alpha^\prime= -0.0135 \pm 0.0074 (stat.) \pm 0.0051 (syst.) GeV^-2. The measurements are compared with perturbative QCD models based on BFKL and DGLAP evolution. The data are found to be compatible with s-channel helicity conservation.
The differential photoproduction cross section DSIG/DT for diffractive J/PSI production.
The J/PSI photoproduction cross section as a function of W for the ABS(T) range 2 to 5 GeV**2.
The J/PSI photoproduction cross section as a function of W for the ABS(T) range 5 to 10 GeV**2.
We report on a measurement of the inclusive cross sections of $\Lambda$ , $\overline\Lambda$ , K 0
Total inclusive hyperon production cross sections for the SIGMA- beam on the Copper target.
Total inclusive hyperon production cross sections for the SIGMA- beam on the Carbon target.
Total inclusive hyperon production cross sections per nucleon for the SIGMA- beam, and the exponent in the cross section parametrization of the form A**POWER.
Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.
Inclusive differential cross section DSIG/DXL for K0S production in the XL interval -0.12 to 0.0 plus the total cross section after extrapolation to the full XL range.
Inclusive differential cross section DSIG/DXL for LAMBDA production in the XL interval -0.12 to 0.0 plus the total cross section after extrapolation to thefull XL range.
Inclusive differential cross section DSIG/DXL for LAMBDABAR production in the XL interval -0.12 to 0.0 plus the total cross section after extrapolation to the full XL range.
We present data from Fermilab experiment E781 (SELEX) on the hadroproduction asymmetry for anti-Lambda_c compared to Lambda_c+ as a function of xF and pt2 distributions for Lambda_c+. These data were measured in the same apparatus using incident pi-, sigma- beams at 600 GeV/c and proton beam at 540 GeV/c. The asymmetry is studied as a function of xF. In the forward hemisphere with xF >= 0.2 both baryon beams exhibit very strong preference for producing charm baryons rather than charm antibaryons, while the pion beam asymmetry is much smaller. In this energy regime the results show that beam fragments play a major role in the kinematics of Lambda_c formation, as suggested by the leading quark picture.
The number of events reconstructed in the signal mass region of LAMBDA/C+ production. Statistical errors only.
The number of events reconstructed in the signal mass region of LAMBDA/CBAR- production. Statistical errors only.
The number of events reconstructed in the signal mass region of LAMBDA/C+ production. Statistical errors only.
None
Total inclusive production cross sections for the SIGMA- beam on the Coppertarget.
Total inclusive production cross sections for the SIGMA- beam on the Carbontarget.
Total inclusive production cross sections per nucleon for the SIGMA- beam, and the exponent in the cross section parametrization of the form A**POWER.
The production of the J/ ψ and ψ ′ charmonia states has been studied, through their dimuon decay, in proton, Oxygen and Sulphur induced reactions, by the NA38 experiment at the CERN SPS. The proton data was collected with beams of 200 and 450 GeV, while the ion beams had an energy of 200 GeV per incident nucleon. The J/ ψ production cross-section per nucleon-nucleon collision exhibits a remarkably continuous pattern, as a function of the product of the mass numbers of the interacting nuclei, from pp up to S-U reactions. The same pattern is observed within S-U collisions, as a function of the collision centrality. While in p-A interactions both charmonia states exhibit the same A-dependence, in S-U collisions the ψ ′ production is very strongly suppressed.
Results of fitting the 200 and 450 GeV J/PSI data separately with a power law parametrization SIG=SIG0*(A*B)**POWER, where A and B are the beam and targetmass numbers. The value obtained from a combined fit is also given, as well as the ratio between the values of SIG0 for the 200 and 450 GeV data sets.
The J/PSI cross sections per nucleon (times the BR to di-muons) rescaled to 200 GeV/nucleon, using the SIG0 ratio detemined in the previous table, and to the cm rapidity window 0 to 1. The errors are combined statistical and systematic.
The ratio between the PSI(3685) and the J/PSI production cross section, times their BR into di-muons, at an incident beam energy of 450 GeV per nucleon. The errors are combined statistical and systematic.
The production of charmed particles by Sigma- of 340 Gev/c momentum was studied in the hyperon beam experiment WA89 at the CERN-SPS, using the Omega-spectrometer. In two data-taking periods in 1993 and 1994 an integrated luminosity of 1600 microb^-1 on copper and carbon targets was recorded. From the reconstruction of 930 +- 90 charm particle decays in 10 decay channels production cross sections for D, antiD, Ds and Lambdac were determined in the region xF>0. Assuming an A^1 dependence of the cross section on the nucleon number, we calculate a total ccbar production cross section of sigma(x_F > 0) = 5.3+- 0.4(stat)+-1.0(syst)+1.0(Xi_c) microb per nucleon. The last term is an upper limit on the unknown contribution from charmed-strange baryon production.
Fits to the DSIG/DXL and DSIG/DPT**2 distributions in the range XL > 0. Theerrors shown are statistical only.. The fits are of the following form:. DSIG/DXL : Const*(1-X)**N. DSIG/DPT**2 : Const*EXP(-B*PT**2).
The production cross sections for anti-charmed and charmed hadrons in the range XL > 0. The Errors are statistical only.
The total CQUARK+CQUARKBAR cross section in the range XL > obtained as the weighted average of the sum of all the measured contributions to the charmed andanti-charmed hadron production in the previous table. second systematic (DSYS) error is due to the uncertainty in the contribution of XI/C production to the cross section.
We report measurements of D ∗± production in interactions between 350 GeV/ c π − particles and nuclei. Reconstruction of the decay D ∗+ → D 0 π + and charge conugate, with D 0 identified via its decays to K − π + and K − π − π + π + , has allowed isolation of a sample of 611 ± 28 D ∗± mesons, produced at positive x F . Assuming a linear A-dependence, the cross-section per nucleon in the region x F > 0 is measured to be 1.41 ± 0.10 ± 0.11 μ b for D ∗+ and 1.84 ± 0.12 ± 0.15 μ b for D ∗− . We present measurements of differential cross-sections with respect to x F and P t 2 , and compare data for D ∗± (vector-meson) production with data for production of charmed pseudoscalar mesons.
No description provided.
Data on D0, DBAR0, D+, and D- meson production are taken from previous publication of this collaboration (see NP B495, 3).
No description provided.
Absolute J/ ψ and ψ ′ production cross sections have been measured at the CERN SPS, with 450 GeV/ c protons incident on a set of C, Al, Cu and W targets. Complementing these values with the results obtained by experiment NA51, which used the same beam and detector with H and D targets, we establish a coherent picture of charmonia production in proton-induced reactions at SPS energies. In particular, we show that the scaling of the J/ ψ cross section with the mass number of the target, A, is well described as A α , with α ψ =0.919±0.015. The ratio between the J/ ψ and ψ ′ yields, in our kinematical window, is found to be independent of A, with α ψ ′ − α ψ =0.014±0.011.
The ratio of the production cross sections, in the di-muon channel. Note that there are wo set of CU and WT data with targets of different lengths. An average values is also given for these.
The J/PSI absolute cross sections, times the BR to di-muons.
The PSI(3685) absolute cross sections, times the BR to di-muons.
Exclusive production of $\rho^0$ and $J/\psi$ mesons in e^+ p collisions has been studied with the ZEUS detector in the kinematic range $0.25 < Q^2 < 50 GeV^2, 20 < W < 167 GeV$ for the $\rho^0$ data and $2 < Q^2 < 40 GeV^2, 50 < W < 150 GeV$ for the $J/\psi$ data. Cross sections for exclusive $\rho^0$ and $J/\psi$ production have been measured as a function of $Q^2, W$ and $t$. The spin-density matrix elements $r^{04}_{00}, r^1_{1-1}$ and $Re r^{5}_{10}$ have been determined for exclusive $\rho^0$ production as well as $r^{04}_{00}$ and $r^{04}_{1-1}$ for exclusive $J/\psi$ production. The results are discussed in the context of theoretical models invoking soft and hard phenomena.
Exclusive RHO0 electro- and photo- production and cross sections as a function of Q**2 from the BPC data set.
Exclusive RHO0 electro- and photo- production cross section as a function of W from the BPC data set.
Exclusive RHO0 electro- and photo- production cross sections as a function of W from the DIS data set.
The complete charge distribution of products from Au nuclei fragmenting in nuclear emulsion at 10.7A GeV has been measured. Multiplicities of produced particles and particles associated with the targe
No description provided.
No description provided.
The interactions of $\bar p$ with D(2), Li(7), C(12), S(32), Cu(64) and Pb(207) nuclei at $40 GeV/c$ were studied by RISC-streamer chamber spectrometer. The yields of $K^0$ mesons and $\Lambda$ and $\bar\Lambda$ hyperons as functions of the target nucleus mass numbers are investigated. The experimental results are compared with model predictions using $FRITIOF-7.02$ program package.
No description provided.
A-dependence of particle yields were fitted to the Y=const*A**power.
The longitudinal momentum spectra of mesons produced in the projectile fragmentation region ofK−p interactions at 110 GeV/c, measured in a bubble chamber experiment, are compared to two fragmentation models related to hadron production by incident leptons. The models give a qualitative description of the data. However, it is found that the mesons having a valence quark in common with the projectile tend to have higher momenta than predicted.
No description provided.
Charmed-meson production by 350 GeV/c π − particles incident on copper and tungsten targets has been studied in the WA92 experiment, performed at the CERN Ω′ spectrometer. Results obtained are reported and discussed. Reconstruction of decays from the set D 0 → K − π + D 0 → K − π − π + π + , D s + → φπ + and charge conjugates has yielded a sample of 7280 ± 108 charmed mesons, produced with χ F > 0, ( χ F ) = 0.18 and〈 p T 2 〉 = 1.86 ( GeV / c ) 2 . Assuming a relationship σ = σ 0 A α between the cross section, σ, per nucleus of mass A and the nucleonic cross section, σ 0 the α value found for the detected charmed particles is 0.95 ± 0.06 ± 0.03. Taking α = 1, the measured cross sections per nucleon for χ F > 0 production are 7.78 ± 0.14 ± 0.52 μ b for D 0 / D 0 , 3.28 ± 0.08 ± 0.29 μ b for D + /D − and 1.29 ± 0.16 ± 0.33 μ b for D s + /D s − . Differential cross sections with respect to χ F and p T 2 have been determined for the various types of charmed meson, and particle-antiparticle asymmetries have been analysed.
No description provided.
No description provided.
Nuclear dependence is fitted by SIG=CONST*A**POWER for CU and WT nuclei.
An experiment performed at Fermilab used double-arm calorimeter triggers to study di-jet production by 400 GeV protons and 200 GeVπ− mesons incident on liquid hydrogen. The observed ratio of positive to negative leading particles in the jets was compared forpp andπp production using a tree level parton scattering model. The results are moderately sensitive to the form of the pion gluon distribution function and yieldx g(x)⋍(1−x)2.75±0.40±0.75.
One parameter function is used for gluon distribution: X*G(X) = C*(1-x)**POWER.
The average charged particle multiplicity, 〈 n ch ( M X 2 )〉, in the reaction K + p→K o X ++ is studied as a function of the mass squared, M X 2 , of the recoil system X and also as a function of the K o transverse momentum, p T , at incident momenta of 5.0, 8.2 and 16.0 GeV/ c . The complete data samples yield distributions which are not independent of c.m. energy squared, s , They exhibit a linear dependence on log ( M X 2 X / M o 2 )[ M o 2 =1 GeV 2 ] with a change in slope occurring for M X 2 ≈ s /2, and do not agree with the corresponding distributions of 〈 n ch 〉 as a function of s for K + p inelastic scattering. Sub-samples of the data for which K o production via beam fragmentation, central production and target fragmentation are expected to be the dominant mechanisms show that, within error, the distribution of 〈 n ch ( M X 2 )〉 versus M X 2 is independent of incident momentum for each sub-sample separately. In particular in the beam fragmentation region the 〈 n ch ( M X 2 )〉 versus M X 2 distribution agrees rather well with that of 〈 n ch 〉 versus s for inelastic K + p interactions. The latter result agrees with recent results on the reactions pp → pX and π − p → pX in the NAL energy range. Evidence is presented for the presence of different production mechanisms in these separate regions.
Two parametrizations are used for fitting of the mean multiplicity of the charged particles : MULT = CONST(C=A) + CONST(C=B)*LOG(M(P=4 5)**2/GEV**2) and MULT = CONST(C=ALPHA)**(M(P=4 5)**2/GEV**2)**POWER.
We present a measurement and comparison of the χc1 and χc2 production cross sections determined from interactions of 300-GeV/c π± and p with a Li target. We find χc1χc2 production ratios of 0.52−0.27+0.57 and 0.08−0.15+0.25 from reactions induced by π± and p, respectively.
The cross section per nucleon.
The cross section per nucleon. The differential cross section is fitted by the equation : D(SIG)/D(PT**2)= CONST*EXP(SLOPE*PT), D(SIG)/D(XL) = CONST*(1-(XL-CONST(C=X0))**2)**POWER(C=1) , and D(SIG)/D(XL) = CONST*(1-ABS(XL-CONST(C=XC)))**POWER(C=2).
The cross section per nucleon. The differential cross section is fitted by the equation : D(SIG)/D(COS(THETA)) = CONST*(1+CONST*COS(THETA)**2), where THETA is the angle between the MU+ and beam momentum in the CHI/C rest frame.
In an experiment performed at Fermilab we have studied the production of high p t hadron jets from 400 GeV/ c pp interactions. A large solid-angle, towered calorimeter was used to trigger and reconstruct the jet events. We report results for inclusive single-jet production and compare those results with QCD predictions and results obtained at the ISR and the SPS Collider.
The invariant distribution is fitted to CONST*(1/PT**POWER)*(1-XT)**POWER.
Results of fitting the differential distributions in x F and p T 2 of D mesons produced in 400 GeV/ c p-p interactions to the form d 2 σ d x F d p T 2 ∝(1−x F ) n exp [−(p T 2 /〈p T 2 〉)] are discussed. The D + distribution is found to be relatively hard [ n =3.1±0.8〈 P t 2 〉=1.32±0.27 (GeV/ c ) 2 ] and the D̄ 0 distribution relatively soft [ n =8.1±1.9,〈 p T 2 〉=0.62±0.14 (GeV/ c ) 2 ] compared to the average for all D's [ n =4.9±0.5,〈 p T 2 〉=0.99±0.10 (GeV/ c ) 2 ]. It is suggested that these distributions could reflect contribution of leading di-quarks in pp collisions. Comparison is made with evidence for leading quarks in charm production in 360 GeV/ cπ − p interactions.
The invariant (C=INV) and non-invariant (C=NON-INV) distributions are fitted to (1-XL)**POWER. Pt distribution is fitted to EXP(-PT**2/SLOPE).
We report results on D 0 and D + production in proton-emulsion interactions at s =38.7 GeV. A fit to the form (1−| x F |) n exp (−bp 2 T ) yields n=6.9 +1.9 −1.8 and b=0.84 +0.10 −0.08 (GeV/ c ) −2 . The total inclusive cross section, is assuming linear A dependence, is measured to be 38±3(stat.) ±13 (sys.) μ b for the D 0 and 38±9±14 μ b for the D + . A comparison of these results with previous measurements indicates that nuclear effects do not strongly influence charm production. The predictions of QCD are in good agreement with our data.
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
Linear A-dependence. Different modes of the charm mesons detection were used (see text for detail).
We measure the differential cross sections with respect to Feynman x ( xF) and transverse momentum ( pT) for π, K, and p-induced charm meson production using fully reconstructed D+, D0, and Ds decays. The shapes of these cross sections are compared to the theoretical predictions for charm quark production of next-to-leading order perturbative QCD using modern parametrizations of the pion and nucleon parton distributions. We observe the differences expected in production induced by projectiles with different gluon distributions, harder distributions being indicated for mesons than for protons.
Additional systematic errors of 6 pct, 6 pct and 9 pct respectively for pi, K and p beams.
Additional systematic errors of 6 pct, 6 pct and 9 pct respectively for pi, K and p beams.
Result of fitting DSIG/dXL spectra with form (1-XL)**POWER.
The scale dependence of the evolution of photoproduction cross sections with the photon-proton centre of mass energy W is studied using low Q~2 < 0.01 GeV~2 e~+p interactions collected by the H1 experiment at HERA. The value of the largest transverse momentum of a charged particle in the photon fragmentation region is used to define the hard scale. The slope of the $W$ dependence of the cross section is observed to increase steeply with increasing transverse momentum. The result is compared to measurements of the Q~2 evolution of the W dependence of the virtual photon-proton cross section. Interpretations in terms of QCD and in terms of Regge phenomenology are discussed.
The gamma p cross section is parameterized as CONST*(W**2)**POWER.
We present total and differential cross sections for charm mesons produced in 600 GeV/ c π - emulsion interactions. Fits to d 2 σ / dx F dp T 2 ∞ (1−| x F |) n exp (- bp T 2 ) for 676 electronically reconstructed D mesons with x F >0 give n =4.25±0.24 ( stat .)±0.23 ( syst .) and b =0.76±0.03±0.03 ( GeV / c ) -2 . The total inclusive D + and D 0 cross sections are σ ( π - N → D ± ; x F >0) = 8.66±0.46±1.96 μb nucleon and σ(π - N→D 0 D 0 ; x F >0)=22.05±1.37±4.82μb nucleonk, where a linear dependence on the mean atomic weight of the target is assumed. These results are compared to next-to-leading order QCD predictions.
Linear A-dependence. Different modes of the charm mesons detection were used (see text for detail). The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
Linear A-dependence.
Charmed mesons, produced on silicon, copper and tungsten by 340 GeV π - , have been identified as peaks in invariant mass distributions. The comparison of the yields of charmed particles originating from interactions in Si, Cu and W allows the mass number dependence of the charm hadroproduction cross section to be measured. Assuming the usual parametrization σ c = σ 0 A α , we find α =0.92±0.06 for charmed mesons with 〈 x F 〉=0.24. We do not find any decrease of α with increasing x F in contrast to the case of the production of particles containing only light quarks.
SI, CU, and WT are used. The cross section is parametrized as : SIG = CONST*A**POWER.
Low mass muon pair production at high P T and low X F studied in pU, OU and SU 200 GeV per nucleon react ions. When energy density or projectile mass are increased, φ production is enhanced as compared with the yield of muon pairs in the mass continuum (1.7< M μμ < 2.4 GeV/ c 2 ), whereas the production of ω and ϱ, experimentally unresolved, remains approximately constant. This φ enhancement is in agreement with predictions based on quark-gluon plasma formation and, together with the previously reported J/Ψ suppression, puts severe constraints on a purely hadronic description of nucleus-nucleus collisions.
The cross sections are parametrized as A**POWER.
Nuclear transparencies measured in exclusive incoherent ρ0 meson production from hydrogen, deuterium, carbon, calcium, and lead in muon-nucleus scattering are reported. The data were obtained with the E665 spectrometer using the Fermilab Tevatron muon beam with a mean beam energy of 470 GeV. Increases in the nuclear transparencies are observed as the virtuality of the photon increases, in qualitative agreement with the expectations of color transparency.
No description provided.
Total and differential cross sections for photoproduction of η mesons from 12 C, 40 Ca, 93 Nb, and nat Pb have been obtained up to 790 MeV incident photon energy at the Mainz Microtron (MAMI) with the TAPS spectrometer. The absorption cross section σ ηN abs = (30 ± 2.5 ± 6)mb of η mesons in nuclear matter and the absorption length λ η = (2.0 ± 0.2 ± 0.4) fm are extracted. No significant depletion of the S 11 (1535) strength in the η photoproduction on nuclei is observed.
THE TOTAL SIG WAS PARAMETRIZED BY A**POWER.
The transverse momentum distributions for\(\rho ^0 (770),f_2 (1270),K*^0 (892),\bar K*^0 (892)\) and ϕ (1020) have been studied in thept region between 2 and 4 GeV/c and central rapidity. The data analysed come from the WA77 experiment at CERN with a 300 GeV/c π− beam incident on a Be target. These distributions are well described by the functionpt−n withn∼8. A sample of simulated events from the Lund Monte Carlo in the same experimental conditions reproduces well the data.
No description provided.
Acceptance corrected tranverse momentum distribution.
Acceptance corrected tranverse momentum distribution.
The total cross sections for the elastic electroproduction of $\rh0$ and $J/\Psi$ mesons for $Q~2$ $>$ 8 GeV$~2$ and $\langle W \rangle \simeq 90$ GeV/c$~2$ are measured at HERA with the H1 detector. The measurements are for an integrated electron$-$proton luminosity of $\simeq$3pb$~{-1}$. The dependences of the total virtual photon$-$proton ($\gamma~* p$) cross sections on $Q~2$, $W$ and the momentum transfer squared to the proton ($t$), and, for the $\rho$, the dependence on the polar decay angle ($\cos \theta~*$), are presented. The $J/\Psi$ : $\rh0$ cross section ratio is determined. The results are discussed in the light of theoretical models and of the interplay of hard and soft physics processes.
Overall EP cross section for M(PI+PI-) < 1.5 GEV.
Overall EP cross section, taking into account the J/PSI --> LEPTON+ LEPTON - branching fraction 0.12.
Integrated EP cross section.
We have analysed a sample of 2.36 million minimum bias events produced in p p collisions at s =630 GeV in the UA1 experiment at the CERN collider. We have studied the production of charged particles with transverse momenta ( p T ) up to 25 GeV/c. The results are in agreement with QCD predictions. The rise of 〈 p T 〉 with charged particle multiplicity may be related to changing production of low p T particles.
No description provided.
No description provided.
No description provided.
We report data on proton-nucleon collisions obtained on Fermilab experiment E711, in which high transverse momentum hadrons are produced near 90° in the proton-nucleon center of mass forming high mass states, using an 800 GeV/c proton beam on targets of beryllium, aluminum, iron, and tungsten. The data presented cover the mass range from 7 to 15 GeV/c2, the three dihadron charge states ++, +-, and --, and parton-parton scattering angles up to cosθ*=0.50. We present the differential mass dihadron cross section, as well as the angular and charge dependence of the measurement. The cross section as a function of the parton-parton scattering angle for the three charge states is shown to vary linearly with the value of the atomic weight. While the angular distributions are shown to be independent of the target type, a small dependence on the charge state of the distributions is observed. The data are shown to be in good agreement with extrapolations from previous measurements and phenomenological QCD calculations.
Atomic weight dependence as function of the parton-parton scattering angle. This angle (theta cm) is defined as the polar angle between the dihadron axis and the beam director in the rest frame of the massive dihadron state. Cross section parameterised as SIG0(MASS**A). Measurements of A are presented here as POWER(N=A,YN=SIG).
Atomic weight dependence as function of the parton-parton scattering angle. This angle (theta cm) is defined as the polar angle between the dihadron axis and the beam director in the rest frame of the massive dihadron state. Cross section parameterised as SIG0(MASS**A). Measurements of A are presented here as POWER(N=A,YN=SIG).
Errors are statistical only.
None
NUCLEUS IS P, C, AL.
No description provided.
We report results from Fermilab experiment E769 on the differential cross sections of D*± charm vector mesons with respect to Feynman-x (xF) and transverse momentum (PT), and on the atomic mass dependence of the production. The D* mesons were produced by a 250 GeV π beam on a target of Be, Al, Cu, and W foils. The dσdxF distribution is fit by the form ((1−xF)n) with n=3.5±0.3±0.1, the dσdPT2 distribution by exp(−b×PT2) with b=0.70±0.07±0.04 GeV−2, and the cross section A dependence by Aα with α=1.00±0.07±0.02. These results are compared to the equivalent parameters for the production of pseudoscalar D0 and D± charm mesons.
Data are in arbitrary units and are the weighted averages bin-by-bin for the 3 D0 modes KPI, K3PI and KPIPI0.
Data are in arbitrary units and are the weighted averages bin-by-bin for the 3 modes KPI, K3PI and KPIPI0.
Results of fit to DSIG/DXL distribution of the form (1-XL)**POWER in the XL range 0.1 to 0.6.
We have used the Fermilab 30-in. bubble-chamber-hybrid spectrometer to study neutral-strange-particle production in the interactions of 200-GeV/c protons and π+ and K+ mesons with nuclei of gold, silver, and magnesium. Average multiplicities and inclusive cross sections for K0 and Λ are measured, and a power law is found to give a good description of their A dependence. The exponent characterizing the A dependence is consistent with being the same for K0 and Λ production, and also the same for proton and π+ beams. Average K0 and Λ multiplicities, as well as their ratio, have been measured as functions of the numbers of projectile collisions νp and secondary collisions νs in the nucleus, and indicate that rescattering contributes significantly to enhancement of Λ production but not to K0 production. The properties of events with multiple K0's or Λ's also corroborate this conclusion. K0 rapidities are in the central region and decrease gently with increasing νp, while Λ rapidities are in the target-fragmentation region and are independent of νp. K0 and Λ multiplicities increase with the rapidity loss of the projectile, but their rapidities do not.
No description provided.
No description provided.
No description provided.
We present results from the initial run of Fermilab experiment E706. The data include incident π− and p beams at 500 GeV/c on Be and Cu targets, and span the kinematic ranges of transverse momentum and rapidity of 3.5≤pT≤10 GeV/c and −0.7≤yc.m.≤0.7, respectively. We have measured cross sections for π0 and direct-photon production, as well as the ηπ0 production ratio. From the data on Be and Cu, we have extracted the nuclear dependence of π0 production, parametrized as Aα. The cross sections are compared with next-to-leading-log QCD predictions for different choices of the QCD momentum scales and several sets of parton distribution functions.
No description provided.
No description provided.
No description provided.
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