19 research outputs found
Inclusive Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions
Inclusive differential cross sections and
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
GeV in the proton-nucleon system. The ratios of differential
cross sections \rklpa and \rllpa are measured to be and , respectively, for \xf . No significant dependence upon the
target material is observed. Within errors, the slopes of the transverse
momentum distributions also show no significant
dependence upon the target material. The dependence of the extrapolated total
cross sections on the atomic mass of the target material is
discussed, and the deduced cross sections per nucleon are
compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table
The QCD transition temperature: results with physical masses in the continuum limit II.
We extend our previous study [Phys. Lett. B643 (2006) 46] of the cross-over
temperatures (T_c) of QCD. We improve our zero temperature analysis by using
physical quark masses and finer lattices. In addition to the kaon decay
constant used for scale setting we determine four quantities (masses of the
\Omega baryon, K^*(892) and \phi(1020) mesons and the pion decay constant)
which are found to agree with experiment. This implies that --independently of
which of these quantities is used to set the overall scale-- the same results
are obtained within a few percent. At finite temperature we use finer lattices
down to a <= 0.1 fm (N_t=12 and N_t=16 at one point). Our new results confirm
completely our previous findings. We compare the results with those of the
'hotQCD' collaboration.Comment: 19 pages, 8 figures, 3 table
Test of internal halo targets in the HERA proton ring
Internal wire targets in the halo of stored proton beams provide a line source of proton-nucleus interactions for highest-rate fixed target experiments. We have studied such internal halo targets at the 820 GeV proton ring of the HERA ep collider. The tests showed that most of the protons in the beam halo -which would otherwise hit the collimators - can be brought to interaction in a relatively thin target wire at distances of 7 to 8 beam widths from the center of the beam. At less than 10% of the HERA total design current, and less than 20% of the current per bunch, interaction rates up to 8 MHz were observed, corresponding to more than 2 interactions per bunch crossing. The halo targets were used in parallel to the HERA luminosity operation; no significant disturbances of the HERA ep experiments, of the machine stability or beam quality were observed. We present data on the steady-state and transient behaviour of interaction rates and discuss the interpretation in terms of a simple beam dynamics model. Issues of short-, medium- and long-term rate fluctuations and of rate stabilization by feedback are addressed. (orig.)Available from TIB Hannover: RA 2999(94-119) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman
Factors Controlling Phytoplankton Blooms in a Temperate Estuary: Nutrient Limitation and Physical Forcing
production via chi() decays in 920-GeV pA interactions
Using data collected by the HERA- B experiment, we have measured the fraction of J / ψ 's produced via radiative χ c decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained R χ c = 0.32±0.06 stat ±0.04 sys for the fraction of J / ψ from χ c decays averaged over proton–carbon and proton–titanium collisions. This result is in agreement with previous measurements and is compared with theoretical predictions
HERA-B: an experiment to study CP violation in the B system using an internal target at the HERA proton ring
After a description of a proposal for using the HERA facility as B factory by means of an internal target the proposal for an experiment is described, where Cp violation is studied in the decay B"0#->#J/#psi#K_S for B's inclusively produced in pp-interactions at 800 GeV/c. Chapter 2 presents details of the internal target and the components of the de. Prototypes of the internal target together with simple trigger and detector systems have been installed in the HERA proton ring since 1992, and have evolved into fairly sophisticated tools; the experience gained from these tests is summarized in chapter 3. Chapter 4 describes the simulation of the detector, its expected performance, and the physics reach of the experiment. Logistics and costs of the proposed experiment are addressed in chapter 5. (orig./HSI)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman