Exclusive J/psi and psi(2S) vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities ...between 2.0 and 4.5 are measured to be sigma sub(pp arrow right J) /psi( arrow right mu + mu -)2.0 < eta sub( mu + or -) < 4.5) = 307 + or - 21 + or - 36 pb, sigma sub(pp arrow right psi(2S)( arrow right mu + mu -))(2.0 < eta sub( mu + or -) < 4.5) = 7.8 + or - 1.3 + or - 1.0 pb, where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The J/psi photoproduction cross-section has been measured as a function of the photon-proton centre-of-mass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction cross-section.
We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP ...eigenstates K+ K-, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06 (syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results correspond to the first observation of CP violation in B0->D(*)CP h0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.
The B 0 a B A= 0 oscillation frequency I m d is measured by the LHCb experiment using a dataset corresponding to an integrated luminosity of 1.0 fb - 1 of protonaproton collisions at s = 7 TeV , and ...is found to be I m d = 0.5156 +/- 0.0051 (stat.) +/- 0.0033 (syst.) ps - 1 . The measurement is based on results from analyses of the decays B 0 a D - pi + (D - a K + pi - pi -) and B 0 a J / I K a 0 (J / I a mu + mu - , K a 0 a K + pi -) and their charge conjugated modes.
The asymmetry in the production cross-section I of D +/- mesons, A P = I (D +) - I (D -) I (D +) + I (D -) , is measured in bins of pseudorapidity IDT and transverse momentum p T within the ...acceptance of the LHCb detector. The result is obtained with a sample of D + a K S 0 pi + decays corresponding to an integrated luminosity of 1.0 fb-1, collected in pp collisions at a centre of mass energy of 7 TeV at the Large Hadron Collider. When integrated over the kinematic range 2.0 < p T < 18.0 GeV / c and 2.20 < IDT < 4.75 , the production asymmetry is A P = (- 0.96 +/- 0.26 +/- 0.18) % . The uncertainties quoted are statistical and systematic, respectively. The result assumes that any direct CP violation in the D + a K S 0 pi + decay is negligible. No significant dependence on IDT or p T is observed.
A binned Dalitz plot analysis of B +/- a D K +/- decays, with D a K S 0 pi + pi - and D a K S 0 K + K - , is performed to measure the CP-violating observables x +/- and y +/- which are sensitive to ...the CKM angle gamma. The analysis exploits 1.0 fb - 1 of data collected by the LHCb experiment. The study makes no model-based assumption on the variation of the strong phase of the D decay amplitude over the Dalitz plot, but uses measurements of this quantity from CLEO-c as input. The values of the parameters are found to be x - = (0.0 +/- 4.3 +/- 1.5 +/- 0.6) X 10 - 2 , y - = (2.7 +/- 5.2 +/- 0.8 +/- 2.3) X 10 - 2 , x + = (- 10.3 +/- 4.5 +/- 1.8 +/- 1.4) X 10 - 2 and y + = (- 0.9 +/- 3.7 +/- 0.8 +/- 3.0) X 10 - 2 . The first, second, and third uncertainties are the statistical, the experimental systematic, and the error associated with the precision of the strong-phase parameters measured at CLEO-c, respectively. These results correspond to gamma = (44 - 38 + 43) degree , with a second solution at gamma a gamma + 180 degree , and r B = 0.07 +/- 0.04 , where r B is the ratio between the suppressed and favoured B decay amplitudes.
Measurement of the effective lifetime Aaij, R; Abellan Beteta, C; Adametz, A ...
Physics letters. B,
10/2012, Letnik:
716, Številka:
3-5
Journal Article
Recenzirano
A precise determination of the effective B s 0 ? K + K - lifetime can be used to constrain contributions from physics beyond the Standard Model in the B s 0 meson system. Conventional approaches ...select B meson decay products that are significantly displaced from the B meson production vertex. As a consequence, B mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural network based trigger and event selection. Using 1.0 fb - 1 of data recorded by the LHCb experiment, the effective B s 0 ? K + K - lifetime is measured as 1.455 +/- 0.046 (stat.) +/- 0.006 (syst.) ps .
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 phi gamma has been measured using an integrated luminosity of 1.0 fb-1 of pp collision data collected by the LHCb ...experiment at a centre-of-mass energy of sqrt(s)=7 TeV. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.23 +/- 0.06(stat.) +/- 0.04(syst.) +/- 0.10(fs/fd), where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for BR(B0 -> K*0 gamma), the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.5 +/- 0.4) x 10^{-5}. The direct CP asymmetry in B0 -> K*0 gamma decays has also been measured with the same data and found to be A(CP)(B0 -> K*0 gamma) = (0.8 +/- 1.7(stat.) +/- 0.9(syst.))%. Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations.
A search for Bs -> mu+ mu- and B0 -> mu+ mu- decays is performed using 1.0 fb^-1 of pp collision data collected at \sqrt{s}=7 TeV with the LHCb experiment at the Large Hadron Collider. For both ...decays the number of observed events is consistent with expectation from background and Standard Model signal predictions. Upper limits on the branching fractions are determined to be BR(Bs -> mu+ mu-) < 4.5 (3.8) x 10^-9 and BR(B0 -> mu+ mu-) < 1.0 (0.81) x 10^-9 at 95% (90%) confidence level.
We present a measurement of the asymmetry A_{CP} between same-sign inclusive dilepton samples ℓ^{+}ℓ^{+} and ℓ^{-}ℓ^{-} (ℓ=e, μ) from semileptonic B decays in ϒ(4S)→BBover ¯ events, using the ...complete data set recorded by the BABAR experiment near the ϒ(4S) resonance, corresponding to 471×10^{6} BBover ¯ pairs. The asymmetry A_{CP} allows comparison between the mixing probabilities P(Bover ¯^{0}→B^{0}) and P(B^{0}→Bover ¯^{0}), and therefore probes CP and T violation. The result, A_{CP}=-3.9±3.5(stat)±1.9(syst)×10^{-3}, is consistent with the standard model expectation.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The relative production rate of ... and B super(0) mesons is determined with the hadronic decays ... and B super(0) arrow ...right D super(-) K super(+). The measurement uses data corresponding to 1.0 fb super(-1) of pp collisions at a centre-of-mass energy of ... TeV recorded in the forward region with the LHCb experiment. The ratio of production rates, f sub( s) /f sub(d), is measured to be 0.238 plus or minus 0.004 plus or minus 0.015 plus or minus 0.021, where the first uncertainty is statistical, the second systematic, and the third theoretical. This is combined with a previous LHCb measurement to obtain f sub(s) /f sub(d)=0.256 plus or minus 0.020. The dependence of f sub(s) /f sub(d) on the transverse momentum and pseudorapidity of the B meson is determined using the decays ... and B super(0) arrow right D super(-) pi super(+). There is evidence for a decrease with increasing transverse momentum, whereas the ratio remains constant as a function of pseudorapidity. In addition, the ratio of branching fractions of the decays B super(0) arrow right D super(-) K super(+) and B super(0) arrow right D super(-) pi super(+) is measured to be 0.0822 plus or minus 0.0011 (stat) plus or minus 0.0025 (syst). Figure not available: see fulltext.
![Exclusive J/[psi] and [psi]...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0954-3899/small "Exclusive J/[psi] and [psi](2S) production in pp collisions at [radical]S = 7 TeV")
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