870 research outputs found
A novel concept for the detection of tau neutrino appearance
A novel concept for the detection of tau neutrinos is presented, potentially
suitable for use in a long-baseline neutrino oscillation experiment. It relies
on the direct identification of the tau leptons produced in charged-current
interactions, by imaging the Cherenkov light that the tau generates in C6F14
liquid. In a simple simulation about half of the tau leptons can be
successfully identified in this way.Comment: 10 pages, 6 figure
Review of and
The current experimental status of the CKM matrix element V_cb and the ratio V_td/V_ts is reviewed. Knowledge of these elements has a strong impact on the unitarity triangle, of interest for studies of CP violation in the B system. The measurements of V_cb from both inclusive semileptonic b decays and the exclusive channel B -> D* l nu are reaching high precision. For V_td/V_ts the strongest upper limit is derived from studies of B-Bbar mixing
Ring-Imaging Cherenkov Detectors for LHCb
The particle identification system proposed for the LHCb experiment is presented. It consists of ring-imaging Cherenkov detectors with three radiator materials, including the novel use of aerogel in an imaging detector. The photodetectors under development are multipixel hybrid photodiodes, which will allow high performance to be achieved due to their excellent single-photon efficiency and high spatial resolution. Significant pion/kaon separation will be possible for isolated tracks with momenta between 1 and 150 GeV/c; the first studies of pattern recognition in regions of high track density are described
Averaging lifetimes for B hadron species
The measurement of the lifetimes of the individual B species are of great interest. Many of these measurements are well below the 10 level of precision. However, in order to reach the precision necessary to test the current theoretical predictions, the results from different experiments need to be averaged. Therefore, the relevant systematic uncertainties of each measurement need to be well defined in order to understand the correlations between the results from different experiments. \par In this paper we discuss the dominant sources of systematic errors which lead to correlations between the different measurements. We point out problems connected with the conventional approach of combining lifetime data and discuss methods which overcome these problems
Beam tests of a large-scale TORCH time-of-flight demonstrator
The TORCH time-of-flight detector is designed to provide particle
identification in the momentum range 2-10 GeV/c over large areas. The detector
exploits prompt Cherenkov light produced by charged particles traversing a 10
mm thick quartz plate. The photons propagate via total internal reflection and
are focused onto a detector plane comprising position-sensitive Micro-Channel
Plate Photo-Multiplier Tubes (MCP-PMT) detectors. The goal is to achieve a
single-photon timing resolution of 70 ps, giving a timing precision of 15 ps
per charged particle by combining the information from around 30 detected
photons. The MCP-PMT detectors have been developed with a commercial partner
(Photek Ltd, UK), leading to the delivery of a square tube of active area 53
53mm with a granularity of 8 128 pixels equivalent. A
large-scale demonstrator of TORCH, having a quartz plate of dimensions 660
1250 10 mm and read out by a pair of MCP-PMTs with custom
readout electronics, has been verified in a test beam campaign at the CERN PS.
Preliminary results indicate that the required performance is close to being
achieved. The anticipated performance of a full-scale TORCH detector at the
LHCb experiment is presented.Comment: 12 pages, 7 figures, Paper submitted to Nuclear Instruments & Methods
in Physics Research, Section A - Special Issue VCI 201
Beam Spot Position Measurement at the LEP Collider
A precise knowledge of the beam spot position is required for many physics topics at LEP2. The movement of the beam spot is studied at LEP1 using beam orbit monitors close to the interaction points and compared with measurements from tracks produced in e+e- collisions. The beam orbit monitors are found to follow the beam spot position well, particularly when corrected for movements of nearby quadrupole magnets. Data from the LEP high energy run of November 1995 are also analysed, and projections made for the prospects at LEP2
Status of the TORCH time-of-flight project
TORCH is a time-of-flight detector, designed to provide charged pi/K particle
identification up to a momentum of 10 GeV/c for a 10 m flight path. To achieve
this level of performance, a time resolution of 15 ps per incident particle is
required. TORCH uses a plane of quartz of 1 cm thickness as a source of
Cherenkov photons, which are then focussed onto square Micro-Channel Plate
Photomultipliers (MCP-PMTs) of active area 53 x 53 mm^2, segmented into 8 x 128
pixels equivalent. A small-scale TORCH demonstrator with a customised MCP-PMT
and associated readout electronics has been successfully operated in a 5 GeV/c
mixed pion/proton beam at the CERN PS facility. Preliminary results indicate
that a single-photon resolution better than 100 ps can be achieved. The
expected performance of a full-scale TORCH detector for the Upgrade II of the
LHCb experiment is also discussed.Comment: 9 pages, 6 figures, Paper submitted to Nuclear and Methods A :
Proceedings of the 10th International Workshop on Ring Imaging Cherenkov
Detectors (RICH 2018), Moscow, Russia, July 29 to August 4 201
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
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