24 research outputs found
Model-independent evidence for contributions to decays
The data sample of decays acquired with the
LHCb detector from 7 and 8~TeV collisions, corresponding to an integrated
luminosity of 3 fb, is inspected for the presence of or
contributions with minimal assumptions about
contributions. It is demonstrated at more than 9 standard deviations that
decays cannot be described with
contributions alone, and that contributions play a dominant role in
this incompatibility. These model-independent results support the previously
obtained model-dependent evidence for charmonium-pentaquark
states in the same data sample.Comment: 21 pages, 12 figures (including the supplemental section added at the
end
Quantum numbers of the state and orbital angular momentum in its decay
Angular correlations in decays, with , and , are used to measure
orbital angular momentum contributions and to determine the value of
the meson. The data correspond to an integrated luminosity of 3.0
fb of proton-proton collisions collected with the LHCb detector. This
determination, for the first time performed without assuming a value for the
orbital angular momentum, confirms the quantum numbers to be .
The is found to decay predominantly through S wave and an upper limit
of at C.L. is set on the fraction of D wave.Comment: 16 pages, 4 figure
Observation of Z production in proton-lead collisions at LHCb
The first observation of Z boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of root(s) N N = 5TeV is presented. The data sample corresponds to an integrated luminosity of 1.6 nb(-1) collected with the LHCb detector. The Z candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above 20 GeV/c. The invariant dimuon mass is restricted to the range 60-120 GeV/c. The Z production cross-section is measured to be sigma(Z ->mu+mu-) (fwd) = 13.5(-4.0)(+5.4)(stat.) +/- 1.2(syst.) nb in the direction of the proton beam and sigma(Z ->mu+mu-) (bwd) = 10.7(-5.1)(+8.4)(stat.) +/- 1.0(syst.) nb in the direction of the lead beam, where the first uncertainty is statistical and the second systematic
Measurement of Upsilon production in pp collisions at \sqrt{s} = 7 TeV
The production of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in
proton-proton collisions at the centre-of-mass energy of sqrt(s)=7 TeV is
studied with the LHCb detector. The analysis is based on a data sample of 25
pb-1 collected at the Large Hadron Collider. The Upsilon mesons are
reconstructed in the decay mode Upsilon -> mu+ mu- and the signal yields are
extracted from a fit to the mu+ mu- invariant mass distributions. The
differential production cross-sections times dimuon branching fractions are
measured as a function of the Upsilon transverse momentum pT and rapidity y,
over the range pT < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times
branching fractions, integrated over these kinematic ranges, are measured to be
sigma(pp -> Upsilon(1S) X) x B(Upsilon(1S)->mu+ mu-) = 2.29 {\pm} 0.01 {\pm}
0.10 -0.37 +0.19 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S)->mu+ mu-) =
0.562 {\pm} 0.007 {\pm} 0.023 -0.092 +0.048 nb, sigma(pp -> Upsilon(3S) X) x
B(Upsilon(3S)->mu+ mu-) = 0.283 {\pm} 0.005 {\pm} 0.012 -0.048 +0.025 nb, where
the first uncertainty is statistical, the second systematic and the third is
due to the unknown polarisation of the three Upsilon states.Comment: 22 pages, 7 figure
Measurement of the branching fraction and angular amplitudes
A search for the decay with is performed with 0.37 fb of collisions at
= 7 TeV collected by the LHCb experiment, finding a \Bs \to J\psi
K^-\pi^+ peak of signal events. The mass spectrum of
the candidates in the peak is dominated by the contribution.
Subtracting the non-resonant component, the branching fraction of
\BsJpsiKst is , where the first
uncertainty is statistical and the second systematic. A fit to the angular
distribution of the decay products yields the \Kst polarization fractions and
Evidence for CP violation in time-integrated D0 -> h-h+ decay rates
A search for time-integrated CP violation in D0 -> h-h+ (h=K, pi) decays is
presented using 0.62 fb^-1 of data collected by LHCb in 2011. The flavor of the
charm meson is determined by the charge of the slow pion in the D*+ -> D0 pi+
and D*- -> D0bar pi- decay chains. The difference in CP asymmetry between D0 ->
K-K+ and D0 -> pi-pi+, Delta ACP = ACP(K-K+) - ACP(pi-pi+), is measured to be
[-0.82 \pm 0.21(stat.) \pm 0.11(syst.)]%. This differs from the hypothesis of
CP conservation by 3.5 standard deviations.Comment: 8 pages, 3 figures, 2 tables; v2 minor updates after journal revie
Measurement of CP violation and constraints on the CKM angle Îł in B± â DK± with D â K0SÏ+Ïâ decays
A model-dependent amplitude analysis of B± â DK± with D â K0
SÏ+Ïâ decays is performed using
protonâproton collision data, corresponding to an integrated luminosity of 1 fbâ1, recorded by LHCb at
a centre-of-mass energy of 7 TeV in 2011. Values of the CP violation observables x± and y±, which are
sensitive to the CKM angle Îł, are measured to be
xâ = +0.027 ± 0.044+0.010 â0.008 ± 0.001,
yâ = +0.013 ± 0.048+0.009 â0.007 ± 0.003,
x+ = â0.084 ± 0.045 ± 0.009 ± 0.005,
y+ = â0.032 ± 0.048+0.010 â0.009 ± 0.008,
where the first uncertainty is statistical, the second systematic and the third arises from the uncertainty of
the D â K0
SÏ+Ïâ amplitude model. The value of Îł is determined to be (84+49
â42)âŠ, including all sources
of uncertainty. Neutral D meson mixing is found to have negligible effect
Descriptions of some new species of spiders from British India
Volume: 13Start Page: 478End Page: 49
Observation of Two New Xi(-)(b) Baryon Resonances
Two structures are observed close to the kinematic threshold in the \u39eb0\u3c0- mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0fb-1, recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content bds are expected in this mass region: the spin-parity JP=(1/2)+ and JP=(3/2)+ states, denoted \u39eb\u2032- and \u39eb 17-. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(\u39eb\u2032-)-m(\u39eb0)-m(\u3c0-)=3.653\ub10.018\ub10.006MeV/c2, m(\u39eb 17-)-m(\u39eb0)-m(\u3c0-)=23.96\ub10.12\ub10.06MeV/c2, \u393(\u39eb 17-)=1.65\ub10.31\ub10.10MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of \u393(\u39eb\u2032-)<0.08MeV at 95% confidence level. Relative production rates of these states are also reported