3,310 research outputs found
The Performance of the LHCb Muon Identification Procedure
This note describes the LHCb offline muon identification procedure and the algorithm parameters tuning using a Monte Carlo sample of B -> J Psi Ks events. The performance is also presented for a sample of b-bbar inclusive events
The Muon Identification Procedure of the LHCb Experiment for the First Data
We present a refined muon identification algorithm for the LHCb experiment suitable for the first period of data taking. The new algorithm is robust against possible inefficiencies of the Muon Detector and takes properly into account the momentum dependence, so it can be tuned with calibration samples and exported to signal samples with different momentum spectra without large corrections. The average performance depends on the momentum spectrum of the analyzed sample: with the current simulation we find for tracks with p > 3 GeV/c in a generic b-inclusive sample a muon identification efficiency of 90 % for a misidentification rate of hadrons and electrons of ~2.4 % (~ 1 % excluding pi's and K's decays in flight). Additional rejection power can be obtained by combining in a proper way the informations coming from all the other subdetectors in a global Likelihood: in this case for a muon identification efficiency of 90 % we find a misidentification rate of ~1.8 % (~ 0.8 % excluding pi's and K's decays in flight
Performance of a multigap RPC prototype for the LHCb muon system
Several technologies are under consideration for the muon system of the LHCb experiment. Resistive Plate Chambers (RPCs) are one of the favourite candidates for the outer areas where the particle fluxes are expected to be at most some kHz/cm/sup 2/. This work describes the results obtained with a multigap RPC prototype under various beam conditions at the CERN facilities. (9 refs)
Performance of the Muon Identification at LHCb
The performance of the muon identification in LHCb is extracted from data
using muons and hadrons produced in J/\psi->\mu\mu, \Lambda->p\pi and
D^{\star}->\pi D0(K\pi) decays. The muon identification procedure is based on
the pattern of hits in the muon chambers. A momentum dependent binary
requirement is used to reduce the probability of hadrons to be misidentified as
muons to the level of 1%, keeping the muon efficiency in the range of 95-98%.
As further refinement, a likelihood is built for the muon and non-muon
hypotheses. Adding a requirement on this likelihood that provides a total muon
efficiency at the level of 93%, the hadron misidentification rates are below
0.6%.Comment: 17 pages, 10 figure
Early hematopoietic stem cell transplantation in a patient with severe mucopolysaccharidosis II : 7 years follow-up
Mucopolysaccharidosis type II (MPS II - Hunter syndrome) is an X-linked lysosomal storage disorder caused by a deficiency in the enzyme iduronate-2 sulfatase (I2S), leading to the accumulation of the glycosaminoglycans, affecting multiple organs and systems. Enzyme replacement therapy does not cross the blood brain barrier, limiting results in neurological forms of the disease. Another option of treatment for severe MPS, hematopoietic stem cell transplantation (HSCT) has become the treatment of choice for the severe form of MPS type I, since it can preserve neurocognition when performed early in the course of the disease. To date, only few studies have examined the long-term outcomes of HSCT in patients with MPS II. We describe the seven-year follow-up of a prenatally diagnosed MPS II boy with positive family history of severe MPS form, submitted to HSCT with umbilical cord blood cells at 70 days of age. Engraftment after 30 days revealed mixed chimerism with 79% donor cells; after 7 years engraftment remains at 80%. I2S activity 30 days post-transplant was low in plasma and normal in leukocytes and the same pattern is observed to date. At age 7 years growth charts are normal and he is very healthy, although mild signs of dysostosis multiplex are present, as well as hearing loss. The neuropsychological evaluation (Wechsler Intelligence Scale for Children - Fourth Edition - WISC-IV), disclosed an IQ of 47. Despite this low measured IQ, the patient continues to show improvements in cognitive, language and motor skills, being quite functional. We believe that HSCT is a therapeutic option for MPS II patients with the severe phenotype, as it could preserve neurocognition or even halt neurodegeneration, provided strict selection criteria are followed
Search for CP violation in D+âÏÏ+ and D+sâK0SÏ+ decays
A search for CP violation in D + â ÏÏ + decays is performed using data collected in 2011 by the LHCb experiment corresponding to an integrated luminosity of 1.0 fbâ1 at a centre of mass energy of 7 TeV. The CP -violating asymmetry is measured to be (â0.04 ± 0.14 ± 0.14)% for candidates with K â K + mass within 20 MeV/c 2 of the Ï meson mass. A search for a CP -violating asymmetry that varies across the Ï mass region of the D + â K â K + Ï + Dalitz plot is also performed, and no evidence for CP violation is found. In addition, the CP asymmetry in the D+sâK0SÏ+ decay is measured to be (0.61 ± 0.83 ± 0.14)%
Differential branching fraction and angular analysis of the decay B0âKâ0ÎŒ+ÎŒâ
The angular distribution and differential branching fraction of the decay B 0â K â0 ÎŒ + ÎŒ â are studied using a data sample, collected by the LHCb experiment in pp collisions at sâ=7 TeV, corresponding to an integrated luminosity of 1.0 fbâ1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Model-independent search for CP violation in D0âKâK+ÏâÏ+ and D0âÏâÏ+Ï+Ïâ decays
A search for CP violation in the phase-space structures of D0 and View the MathML source decays to the final states KâK+ÏâÏ+ and ÏâÏ+Ï+Ïâ is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fbâ1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the KâK+ÏâÏ+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the ÏâÏ+Ï+Ïâ final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity
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