20 research outputs found
Antiproton Production in Collisions at AGS Energies
Inclusive and semi-inclusive measurements are presented for antiproton
() production in proton-nucleus collisions at the AGS. The inclusive
yields per event increase strongly with increasing beam energy and decrease
slightly with increasing target mass. The yield in 17.5 GeV/c p+Au
collisions decreases with grey track multiplicity, , for ,
consistent with annihilation within the target nucleus. The relationship
between and the number of scatterings of the proton in the nucleus is
used to estimate the annihilation cross section in the nuclear
medium. The resulting cross section is at least a factor of five smaller than
the free annihilation cross section when assuming a small or
negligible formation time. Only with a long formation time can the data be
described with the free annihilation cross section.Comment: 8 pages, 6 figure
Semi-Inclusive Lambda and Kshort Production in p-Au Collisions at 17.5 GeV/c
The first detailed measurements of the centrality dependence of strangeness
production in p-A collisions are presented. Lambda and Kshort dn/dy
distributions from 17.5 GeV/c p-Au collisions are shown as a function of "grey"
track multiplicity and the estimated number of collisions, nu, made by the
proton. The nu dependence of the Lambda yield deviates from a scaling of p-p
data by the number of participants, increasing faster than this scaling for
nu<=5 and saturating for larger nu. A slower growth in Kshort multiplicity with
nu is observed, consistent with a weaker nu dependence of K-Kbar production
than Y-K production.Comment: 5 pages, 3 figures, formatted with RevTex, current version has
enlarged figure catpion
Inclusive Soft Pion Production from 12.3 and 17.5 GeV/c Protons on Be, Cu and Au
Differential cross-sections are presented for the inclusive production of
charged pions in the momentum range 0.1 to 1.2 GeV/c in interactions of 12.3
and 17.5 GeV/c protons with Be, Cu, and Au targets. The measurements were made
by Experiment 910 at the Alternating Gradient Synchrotron in Brookhaven
National Laboratory. The cross-sections are presented as a function of pion
total momentum and production polar angle with respect to the beam.Comment: 14 pages, 8 figure
Cross-Sections of Large-Angle Hadron Production in Proton- and Pion-Nucleus Interactions III: Tantalum Nuclei and Beam Momenta from +/-3 Gev/c to +/-15 Gev/c
We report on double-differential inclusive cross-sections of the production
of secondary protons, charged pions, and deuterons, in the interactions with a
5% nuclear interaction length thick stationary tantalum target, of proton and
pion beams with momentum from +/-3 GeV/c to +/-15 GeV/c. Results are given for
secondary particles with production angles between 20 and 125 degrees. They are
of particular relevance for the optimization of the design parameters of the
proton driver of a neutrino factory.Comment: 68 pages, 12 figures, corrections in v2: added 'HARP -CDP group' to
author name, corrected two typos in Table 4 (last two p values for 65-90
degrees were all 0.972
Systematic Study of the Kaon to Pion Multiplicity Ratios in Heavy-Ion Collisions
We present a systematic study of the kaon to pion multiplicity ratios (K+/pi+
and K-/pi-) in heavy-ion collisions from AGS to RHIC energy using the
Relativistic Quantum Molecular Dynamics (RQMD) model. The model satisfactorily
describes the available experimental data on K+/pi+ and K-/pi-. Within the
model, we find that the strong increase of the ratios with the number of
participants is mainly due to hadronic rescattering of produced mesons with
ingoing baryons and their resonances. The enhancement of K/pi in heavy-ion
collisions with respect to elementary p+p interactions is larger at AGS energy
than SPS energy, and decreases smoothly with bombarding energy. The total
multiplicity ratios at RHIC energy are predicted by RQMD to be K+/pi+ = 0.19
and K-/pi- = 0.15.Comment: 10 pages, 8 figures, RevTeX style. A section is added to discuss
effects of rope formatio
Measurement of the production of charged pions by protons on a tantalum target
A measurement of the double-differential cross-section for the production of
charged pions in proton--tantalum collisions emitted at large angles from the
incoming beam direction is presented. The data were taken in 2002 with the HARP
detector in the T9 beam line of the CERN PS. The pions were produced by proton
beams in a momentum range from 3 \GeVc to 12 \GeVc hitting a tantalum target
with a thickness of 5% of a nuclear interaction length. The angular and
momentum range covered by the experiment (100 \MeVc \le p < 800 \MeVc and
0.35 \rad \le \theta <2.15 \rad) is of particular importance for the design
of a neutrino factory. The produced particles were detected using a
small-radius cylindrical time projection chamber (TPC) placed in a solenoidal
magnet. Track recognition, momentum determination and particle identification
were all performed based on the measurements made with the TPC. An elaborate
system of detectors in the beam line ensured the identification of the incident
particles. Results are shown for the double-differential cross-sections
at four incident
proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). In addition, the
pion yields within the acceptance of typical neutrino factory designs are shown
as a function of beam momentum. The measurement of these yields within a single
experiment eliminates most systematic errors in the comparison between rates at
different beam momenta and between positive and negative pion production.Comment: 49 pages, 31 figures. Version accepted for publication on Eur. Phys.
J.
High-p_T pion and kaon production in relativistic nuclear collisions
High-p_T pion and kaon production is studied in relativistic proton-proton,
proton-nucleus, and nucleus-nucleus collisions in a wide energy range. Cross
sections are calculated based on perturbative QCD, augmented by a
phenomenological transverse momentum distribution of partons (``intrinsic
k_T''). An energy dependent width of the transverse momentum distribution is
extracted from pion and charged hadron production data in
proton-proton/proton-antiproton collisions. Effects of multiscattering and
shadowing in the strongly interacting medium are taken into account.
Enhancement of the transverse momentum width is introduced and parameterized to
explain the Cronin effect. In collisions between heavy nuclei, the model
over-predicts central pion production cross sections (more significantly at
higher energies), hinting at the presence of jet quenching. Predictions are
made for proton-nucleus and nucleus-nucleus collisions at RHIC energies.Comment: 26 pages in Latex, 19 EPS figure
Large-angle production of charged pions by 3 GeV/c - 12.9 GeV/c protons on beryllium, aluminium and lead targets
Measurements of the double-differential production cross-section
in the range of momentum 100 \MeVc \leq p < 800 \MeVc and angle 0.35 \rad
\leq \theta < 2.15 \rad in proton--beryllium, proton--aluminium and
proton--lead collisions are presented. The data were taken with the HARP
detector in the T9 beam line of the CERN PS. The pions were produced by proton
beams in a momentum range from 3 \GeVc to 12.9 \GeVc hitting a target with a
thickness of 5% of a nuclear interaction length. The tracking and
identification of the produced particles was performed using a small-radius
cylindrical time projection chamber (TPC) placed inside a solenoidal magnet.
Incident particles were identified by an elaborate system of beam detectors.
Results are obtained for the double-differential cross-sections at six incident
proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc, 8.9 \GeVc (Be only), 12 \GeVc
and 12.9 \GeVc (Al only)) and compared to previously available data
Forward pi+/- production in p-O2 and p-N2 interactions at 12 GeV/c
Measurements of double-differential charged pion production cross-sections in
interactions of 12 GeV/c protons on O_2 and N_2 thin targets are presented in
the kinematic range 0.5 GeV/c < p_{\pi} < 8 GeV/c and 50 mrad < \theta_{\pi} <
250 mrad (in the laboratory frame) and are compared with p--C results. For
p--N_2 (p--O_2) interactions the analysis is performed using 38576 (7522)
reconstructed secondary pions. The analysis uses the beam instrumentation and
the forward spectrometer of the HARP experiment at CERN PS. The measured
cross-sections have a direct impact on the precise calculation of atmospheric
neutrino fluxes and on the improved reliability of extensive air shower
simulations by reducing the uncertainties of hadronic interaction models in the
low energy range. In particular, the present results allow the common
hypothesis that p--C data can be used to predict the p--N_2 and p--O_2 pion
production cross-sections to be tested