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

Reconstruction of the decay B"-#->#D_1"o(2414)#pi#"-

We present the results of a partial reconstruction of the decay channel B"-#->#D_J"("*")"0#pi#"- performed using the ARGUS detector operating at the e"+e"- storage-ring DORIS II. In the context of this paper, D_J"("*")"0 is an L=1 excited charm meson decaying to D"*"+#pi#"-. The measured product of branching ratios is Br(B"-#->#D_1"0(2414)#pi#"-).Br((D_1"0#->#D"*"+#pi#"-)=(0.17#+-#0.05#+-#0.04)% where the first error is statistical and the second systematic. No evidence for the decay B"-#->#D_2"*"0(2459)#pi#"- is observed. We calculate the upper limit Br(B"-#->#D_2"*"0(2459)#pi#"-).Br(D_2"*"0#->#D"*"+#pi#"-)<0.07% at the 90% confidence level. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(94-069) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

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