2,271 research outputs found
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
Performance of the LHCb muon system with cosmic rays
The LHCb Muon system performance is presented using cosmic ray events
collected in 2009. These events allowed to test and optimize the detector
configuration before the LHC start. The space and time alignment and the
measurement of chamber efficiency, time resolution and cluster size are
described in detail. The results are in agreement with the expected detector
performance.Comment: Submitted to JINST and accepte
Dalitz Plot Analysis of the Decay D^+ --> K^- pi^+ pi^+ and Indication of a Low-Mass Scalar K pi Resonance
We study the Dalitz plot of the decay D^+ --> K^- pi^+ pi^+ with a sample of
15090 events from Fermilab experiment E791. Modeling the decay amplitude as the
coherent sum of known K pi resonances and a uniform nonresonant term, we do not
obtain an acceptable fit. If we allow the mass and width of the K^*_0(1430) to
float, we obtain values consistent with those from PDG but the chi^2 per degree
of freedom of the fit is still unsatisfactory. A good fit is found when we
allow for the presence of an additional scalar resonance, with mass 797 +/- 19
+/- 43 MeV/c^2 and width 410 +/- 43 +/- 87 MeV/c^2. The mass and width of the
K^*_0(1430) become 1459 +/- 7 +/- 5 MeV/c^2 and 175 +/- 12 +/- 12 MeV/c^2,
respectively. Our results provide new information on the scalar sector in
hadron spectroscopy.Comment: Accepted for publication in Physical Review Letter
Experimental evidence for a light and broad scalar resonance in decay
From a sample of decay, we find
. Using a coherent amplitude analysis
to fit the Dalitz plot of this decays, we find strong evidence that a scalar
resonance of mass MeV/ and width MeV/ accounts for approximately half of all decays.Comment: 10 pages, 3 eps figure
Search for CP Violation in the decays D+ -> K_S pi+ and D+ -> K_S K+
A high statistics sample of photo-produced charm from the FOCUS(E831)
experiment at Fermilab has been used to search for direct CP violation in the
decays D+->K_S pi+ and D+ -> K_S K+. We have measured the following asymmetry
parameters relative to D+->K-pi+pi+: A_CP(K_S pi+) = (-1.6 +/- 1.5 +/- 0.9)%,
A_CP(K_S K+) = (+6.9 +/- 6.0 +/- 1.5)% and A_CP(K_S K+) = (+7.1 +/- 6.1 +/-
1.2)% relative to D+->K_S pi+. The first errors quoted are statistical and the
second are systematic. We also measure the relative branching ratios:
\Gamma(D+->\bar{K0}pi+)/\Gamma(D+->K-pi+pi+) = (30.60 +/- 0.46 +/- 0.32)%,
\Gamma(D+->\bar{K0}K+)/\Gamma(D+->K-pi+pi+) = (6.04 +/- 0.35 +/- 0.30)% and
\Gamma(D+->\bar{K0}K+)/\Gamma(D+->\bar{K0}pi+) = (19.96 +/- 1.19 +/- 0.96)%.Comment: 4 pages, 3 figure
Measurement of the D+ and Ds+ decays into K+K-K+
We present the first clear observation of the doubly Cabibbo suppressed decay
D+ --> K-K+K+ and the first observation of the singly Cabibbo suppressed decay
Ds+ --> K-K+K+. These signals have been obtained by analyzing the high
statistics sample of photoproduced charm particles of the FOCUS(E831)
experiment at Fermilab. We measure the following relative branching ratios:
Gamma(D+ --> K-K+K+)/Gamma(D+ --> K-pi+pi+) = (9.49 +/- 2.17(statistical) +/-
0.22(systematic))x10^-4 and Gamma(Ds+ --> K-K+K+)/Gamma(Ds+ --> K-K+pi+) =
(8.95 +/- 2.12(statistical) +2.24(syst.) -2.31(syst.))x10^-3.Comment: 10 pages, 8 figure
A Non-parametric Approach to the D+ to K*0bar mu+ nu Form Factors
Using a large sample of D+ -> K- pi+ mu+ nu decays collected by the FOCUS
photoproduction experiment at Fermilab, we present the first measurements of
the helicity basis form factors free from the assumption of spectroscopic pole
dominance. We also present the first information on the form factor that
controls the s-wave interference discussed in a previous paper by the FOCUS
collaboration. We find reasonable agreement with the usual assumption of
spectroscopic pole dominance and measured form factor ratios.Comment: 14 pages, 5 figures, and 2 tables. We updated the previous version by
changing some words, removing one plot, and adding two tables. These changes
are mostly stylisti
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