The production of J/ psi pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of 37.5 pb-1 collected with the LHCb detector. The ...production cross-section for pairs with both J/ psi in the rapidity range 2<yJ/ psi <4.5 and transverse momentum p super(J/ psi ) sub(T) < 10 GeV/c is sigma J/ psi J/ psi =5.1+/-1.0+/-1. 1 nb, where the first uncertainty is statistical and the second systematic.
First observation of the decay Aaij, R; Abellan Beteta, C; Adeva, B ...
Physics letters. B,
03/2012, Letnik:
709, Številka:
1-2
Journal Article
Recenzirano
The first observation of the decay B s 0 arrow right K * 0 K macr * 0 is reported using 35 pb - 1 of data collected by LHCb in proton-proton collisions at a centre-of-mass energy of 7 TeV. A total of ...49.8 +/- 7.5 B s 0 arrow right ( K + pi - ) ( K - pi + ) events are observed within +/- 50 MeV / c 2 of the B s 0 mass and 746 MeV / c 2 < m K pi < 1046 MeV / c 2 , mostly coming from a resonant B s 0 arrow right K * 0 K macr * 0 signal. The branching fraction and the CP-averaged K * 0 longitudinal polarization fraction are measured to be B ( B s 0 arrow right K * 0 K macr * 0 ) = ( 2.81 +/- 0.46 ( stat. ) +/- 0.45 ( syst. ) +/- 0.34 ( f s / f d ) ) 10 - 5 and f L = 0.31 +/- 0.12 ( stat. ) +/- 0.04 ( syst. ) .
Search for the rare decays and Aaij, R; Abellan Beteta, C; Adeva, B ...
Physics letters. B,
02/2012, Letnik:
708, Številka:
1-2
Journal Article
Recenzirano
A search for the decays B s 0 arrow right mu + mu - and B 0 arrow right mu + mu - is performed with 0.37 fb-1 of pp collisions at s = 7 TeV collected by the LHCb experiment in 2011. The upper limits ...on the branching fractions are B ( B s 0 arrow right mu + mu - ) < 1.6 10 - 8 and B ( B 0 arrow right mu + mu - ) < 3.6 10 - 9 at 95% confidence level. A combination of these results with the LHCb limits obtained with the 2010 dataset leads to B ( B s 0 arrow right mu + mu - ) < 1.4 10 - 8 and B ( B 0 arrow right mu + mu - ) < 3.2 10 - 9 at 95% confidence level.
Measurement of the effective lifetime Aaij, R; Abellan Beteta, C; Adeva, B ...
Physics letters. B,
02/2012, Letnik:
707, Številka:
3-4
Journal Article
Recenzirano
A measurement of the effective B s 0 arrow right K + K - lifetime is presented using approximately 37 pb - 1 of data collected by LHCb during 2010. This quantity can be used to put constraints on ...contributions from processes beyond the Standard Model in the B s 0 meson system and is determined by two complementary approaches as tau K K = 1.440 +/- 0.096 ( stat ) +/- 0.008 ( syst ) +/- 0.003 ( model ) ps .
The B s 0 - B macr s 0 oscillation frequency Delta m s is measured with 36 pb-1 of data collected in pp collisions at s = 7 TeV by the LHCb experiment at the Large Hadron Collider. A total of 1381 B ...s 0 arrow right D s - pi + and B s 0 arrow right D s - pi + pi - pi + signal decays are reconstructed, with average decay time resolutions of 44 fs and 36 fs, respectively. An oscillation signal with a statistical significance of 4.6 sigma is observed. The measured oscillation frequency is Delta m s = 17.63 +/- 0.11 ( stat ) +/- 0.02 ( syst ) ps - 1 .
The cross-section for inclusive phi meson production in pp collisions at a centre-of-mass energy of inline image has been measured with the LHCb detector at the Large Hadron Collider. The ...differential cross-section is measured as a function of the phi transverse momentum p sub(T and rapidity y in the region 0.6p) sub(T)5.0 GeV/c and 2.44y4.06. The cross-section for inclusive phi production in this kinematic range is inline image, where the first systematic uncertainty depends on the p sub(T and y region and the second is related to the overall scale. Predictions based on the Pythia 6.4 generator underestimate the cross-section.)
A search for the decays inline imageinline image and Bsuper0--microsuper+microsuper- is performed with about 37 pbsuper-1 of pp collisions at inline imageinline image collected by the LHCb experiment ...at the Large Hadron Collider at CERN. The observed numbers of events are consistent with the background expectations. The resulting upper limits on the branching ratios are inline imageinline image and inline imageinline image at 95% confidence level.
Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the hadronic decay inline image is observed. This CP eigenstate mode could be used to ...measure mixing-induced CP violation in the inline image system. Using a fit to the pi super(+) pi super(-) mass spectrum with interfering resonances gives inline image. In the interval +/-90 MeV around 980 MeV, corresponding to approximately two full f sub(0 widths we also find inline image, where in both cases the uncertainties are statistical and systematic, respectively.)
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