1,559 research outputs found
The HERA-B Ring Imaging Cherenkov Counter
The HERA-B RICH uses a radiation path length of 2.8 m in C_4F_10 gas and a
large 24 square meters spherical mirror for imaging Cherenkov rings. The photon
detector consists of 2240 Hamamatsu multi-anode photomultipliers with about
27000 channels. A 2:1 reducing two-lens telescope in front of each PMT
increases the sensitive area at the expense of increased pixel size, resulting
in a contribution to the resolution which roughly matches that of dispersion.
The counter was completed in January of 1999, and its performance has been
steady and reliable over the years it has been in operation. The design
performance of the RICH was fully reached: the average number of detected
photons in the RICH for a beta=1 particle was found to be 33 with a single hit
resolution of 0.7 mrad and 1 mrad in the fine and coarse granularity regions,
respectively.Comment: 29 pages, 23 figure
Tests of a proximity focusing RICH with aerogel as radiator
Using aerogel as radiator and multianode PMTs for photon detection, a
proximity focusing Cherenkov ring imaging detector has been constructed and
tested in the KEK 2 beam. The aim is to experimentally study the basic
parameters such as resolution of the single photon Cherenkov angle and number
of detected photons per ring. The resolution obtained is well approximated by
estimates of contributions from pixel size and emission point uncertainty. The
number of detected photons per Cherenkov ring is in good agreement with
estimates based on aerogel and detector characteristics. The values obtained
turn out to be rather low, mainly due to Rayleigh scattering and to the
relatively large dead space between the photocathodes. A light collection
system or a higher fraction of the photomultiplier active area, together with
better quality aerogels are expected to improve the situation. The reduction of
Cherenkov yield, for charged particle impact in the vicinity of the aerogel
tile side wall, has also been measured.Comment: 4 pages, 8 figure
A novel type of proximity focusing RICH counter with multiple refractive index aerogel radiator
A proximity focusing ring imaging Cherenkov detector, with the radiator
consisting of two or more aerogel layers of different refractive indices, has
been tested in 1-4 GeV/c pion beams at KEK. Essentially, a multiple refractive
index aerogel radiator allows for an increase in Cherenkov photon yield on
account of the increase in overall radiator thickness, while avoiding the
simultaneous degradation in single photon angular resolution associated with
the increased uncertainty of the emission point. With the refractive index of
consecutive layers suitably increasing in the downstream direction, one may
achieve overlapping of the Cherenkov rings from a single charged particle. In
the opposite case of decreasing refractive index, one may obtain well separated
rings. In the former combination an approximately 40% increase in photon yield
is accompanied with just a minor degradation in single photon angular
resolution. The impact of this improvement on the pion/kaon separation at the
upgraded Belle detector is discussed.Comment: submitted to Nucl. Instr. Meth.
LAPPD operation using ToFPETv2 PETSYS ASIC
Single photon sensitive detectors used in high energy physics are, in some
applications, required to cover very large areas, and more specifically in very
strong demand with an ever finer imaging and timing capability for Cherenkov
Ring Imaging Detector (RICH) configurations. We are evaluating the Large Area
Picosecond Photo-detector (LAPPD) produced by INCOM company, as a possible
candidate for future RICH detector upgrades. In this work we perform tests on
the first generation device, which is capacitively coupled to a custom designed
anode back plane, consisting of various pixels and strips varying in size, that
allows for connecting various readout systems such as standard laboratory
equipment, as well as the TOFPET2 ASIC from PETsys company [2]. Our aim is to
evaluate what can be achieved by merging currently available technology, in
order to find directions for future developments adapted for specific uses.Comment: Twepp 2022 workshop proceeding
Readout ASICs and Electronics for the 144-channel HAPDs for the Aerogel RICH at Belle II
AbstractThe particle identification (PID) device in the endcap of the Belle detector will be upgraded to a ring imaging Cherenkov counter (RICH) using aerogel as a radiator at the Belle II experiment. We develop the electronics to read out the 70,000 channels of hit information from the 144-channel hybrid avalanche photodetectors (HAPD), of the aerogel RICH detector. A readout ASIC is developed to digitize the HAPD signals, and was used in a beam test with the prototype detector. The performance and plan of the ASIC is reported in this study. We have also designed the readout electronics for the aerogel RICH, which consist of front-end boards with the ASICs merger boards to collect data from the front-end boards. A front-end board that fits in the actual available space for the aerogel RICH electronics was produced
Aging Studies for the Large Honeycomb Drift Tube System of the Outer Tracker of HERA-B
The HERA-B Outer Tracker consists of drift tubes folded from polycarbonate
foil and is operated with Ar/CF4/CO2 as drift gas. The detector has to stand
radiation levels which are similar to LHC conditions. The first prototypes
exposed to radiation in HERA-B suffered severe radiation damage due to the
development of self-sustaining currents (Malter effect). In a subsequent
extended R&D program major changes to the original concept for the drift tubes
(surface conductivity, drift gas, production materials) have been developed and
validated for use in harsh radiation environments. In the test program various
aging effects (like Malter currents, gain loss due to anode aging and etching
of the anode gold surface) have been observed and cures by tuning of operation
parameters have been developed.Comment: 14 pages, 6 figures, to be published in the Proceedings of the
International Workshop On Aging Phenomena In Gaseous Detectors, 2-5 Oct 2001,
Hamburg, German
Measurements of Branching Fractions and Polarization in B > K^* rho Decays
We present results of a study of the charmless vector-vector decays B^0 ->
K^{*0} rho^0 and B^+ ->K^{*0} rho^+. The results are based on a 140 fb^{-1}
data sample collected by the Belle detector at the KEKB asymmetric e^+e^-
collider. We obtain the branching fraction B(B^+ -> K^{*0} rho^+)=(6.6 +-
2.2(stat.) +- 0.8 (syst.)) x 10^{-6}, and set upper limits on the branching
fractions B(B^0 -> K^{*0} rho^0) f_0(980)
K^{*0})<5.2 x 10^{-6}. We also perform a helicity analysis of the rho and K^*
vector mesons in the decay B^+ -> K^{*0} rho^+, and obtain the longitudinal
polarization fraction R_0(B^+ -> K^{*0} rho^+)=0.50 +-
0.19(stat.)+0.05-0.07}(syst.).Comment: 11 pages, 4 figures, submitted to ICHEP04, Beijing, Chin
Observation of B+->Lambda_c+Lambda_c-K+ and B0->Lambda_c+Lambda_c^-K0 decays
We report first measurements of the doubly charmed baryonic B decays
B->Lambda_c+Lambda_c-K. The B+->Lambda_c+Lambda_c-K+ decay is observed with a
branching fraction of (6.5+1.0-0.9+-1.1+-3.4)x10^{-4} and a statistical
significance of 15.4sigma. The B0->Lambda_c+Lambda_c-K0 decay is observed with
a branching fraction of (7.9+2.9-2.3+-1.2+-4.2)x10^{-4} and a statistical
significance of 6.6sigma. The branching fraction errors are statistical,
systematic, and the error resulting from the uncertainty of Lambda_c+->pK-pi+
decay branching fraction. The analysis is based on 357fb-1 of data accumulated
at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e+e-
collider.Comment: 10 pages, 3 figure
Improved measurement of time-dependent CP violation in B0 -> J/Psi pi0 decays
We report improved measurements of time-dependent CP violation parameters for
decay. This analysis is based on 535 million
pairs accumulated at the resonance with the Belle
detector at the KEKB asymmetric-energy e^+e^- collider. From the distribution
of proper time intervals between the two B decays, we obtain the following CP
violation parameters and , which are consistent with Standard Model
expectations.Comment: Resubmitted to PRD(RC), including 4 figures, 6pages Revision has been
made according to communication with PRD referee
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