Bottom baryons decaying to a J/ψ meson and a hyperon are reconstructed using 1.0 fb(-1) of data collected in 2011 with the LHCb detector. Significant Λ(b)(0) → J/ψΛ, Ξ(b((-) → J/ψΞ(-) and Ω(b)(-) → ...J/ψΩ(-) signals are observed and the corresponding masses are measured to be M(Λ(b)(0))=5619.53 ± 0.13(stat.) ± 0.45(syst.) MeV/c(2), M(Ξ(b)(-)) = 5795.8 ± 0.9(stat.) ± 0.4(syst.) MeV/c(2), M(Ω(b)(-)) = 6046.0 ± 2.2(stat.) ± 0.5(syst.) MeV/c(2) , while the differences with respect to the Λ(b)(0) mass are M(Ξ(b)(-))-M(Λ(b)(0))=176.2 ± 0.9(stat.) ± 0.1(syst.) MeV/c(2), M(Ω(b)(-))-M(Λ(b)(0))=426.4 ± 2.2(stat.) ± 0.4(syst.) MeV/c(2). These are the most precise mass measurements of the Λ(b)(0), Ξ(b)(-) and Ω(b)(-) baryons to date. Averaging the above Λ(b)(0) mass measurement with that published by LHCb using 35 pb(-1) of data collected in 2010 yields M(Λ(b)(0)) = 5619.44 ± 0.13(stat.)± 0.38(syst.) MeV/c(2).
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract The production cross-sections of B mesons are measured in pp collisions at a centre-of-mass energy of 7 TeV, using ...data collected with the LHCb detector corresponding to a integrated luminosity of 0.36 fb^sup -1^. The B ^sup +^, B ^sup 0^ and ... mesons are reconstructed in the exclusive decays B ^sup +^ arrow right J/psiK ^sup +^, B ^sup 0^ arrow right J/psiK ^sup *0^ and ..., with J/psi arrow right mu ^sup +^ mu ^sup -^, K ^sup *0^ arrow right K ^sup +^pi^sup -^ and arrow right K ^sup +^ K ^sup -^. The differential cross-sections are measured as functions of B meson transverse momentum p ^sub T^ and rapidity y, in the range 0 < p ^sub T^ < 40 GeV/c and 2.0 < y < 4.5. The integrated cross-sections in the same p ^sub T^ and y ranges, including charge-conjugate states, are measured to be ...where the third uncertainty arises from the pre-existing branching fraction measurements. Figure not available: see fulltext.
Observation of D0-D0 oscillations Abellan Beteta, C; Adametz, A; Alves, Jr, A A ...
Physical review letters,
2013-Mar-08, Letnik:
110, Številka:
10
Journal Article
Recenzirano
Odprti dostop
We report a measurement of the time-dependent ratio of D(0) → K(+) π- to D(0) → K(-) π(+) decay rates in D(*+)-tagged events using 1.0 fb(-1) of integrated luminosity recorded by the LHCb experiment. ...We measure the mixing parameters x('2) = (-0.9 ± 1.3) × 10(-4), y' = (7.2 ± 2.4) × 10(-3), and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates R(D) = (3.52 ± 0.15) × 10^{-3}, where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D0-D0 oscillations from a single measurement.
The charmless decays B± → K+ K- π± and B± → π+ π- π± are reconstructed in a data set of pp collisions with an integrated luminosity of 1.0 fb(-1) and center-of-mass energy of 7 TeV, collected by ...LHCb in 2011. The inclusive charge asymmetries of these modes are measured to be A(CP)(B± → K+ K- π±) = -0.141±0.040 (stat)±0.018 (syst)±0.007(J/ψ K±) and A(CP)(B± → π+ π- π±) = 0.117±0.021 (stat)±0.009 (syst)±0.007(J/ψ K±), where the third uncertainty is due to the CP asymmetry of the B± → J/ψK± reference mode. In addition to the inclusive CP asymmetries, larger asymmetries are observed in localized regions of phase space.
A
bstract
Using three- and four-body decays of
D
mesons produced in semileptonic
b
-hadron decays, precision measurements of
D
meson mass differences are made together with a measurement of the
D
0
...mass. The measurements are based on a dataset corresponding to an integrated luminosity of 1
.
0 fb
−1
collected in
pp
collisions at 7 TeV. Using the decay
D
0
→
K
+
K
−
K
−
π
+
, the
D
0
mass is measured to be
The mass differences
are measured using the
D
0
→
K
+
K
−
π
+
π
−
and
modes.
This Letter presents a study of the flavor-changing neutral current radiative B±→K±π∓π±γ decays performed using data collected in proton-proton collisions with the LHCb detector at 7 and 8 TeV ...center-of-mass energies. In this sample, corresponding to an integrated luminosity of 3 fb-1, nearly 14 000 signal events are reconstructed and selected, containing all possible intermediate resonances with a K±π∓π± final state in the 1.1,1.9 GeV/c2 mass range. The distribution of the angle of the photon direction with respect to the plane defined by the final-state hadrons in their rest frame is studied in intervals of K±π∓π± mass and the asymmetry between the number of signal events found on each side of the plane is obtained. The first direct observation of the photon polarization in the b→sγ transition is reported with a significance of 5.2σ.
Measurements of charm mixing parameters from the decay-time-dependent ratio of D0 → K+ π- to D0 → K- π+ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3 ...fb(-1) of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP ) symmetry, the mixing parameters are determined to be x'2=(5.5±4.9)×10(-5), y'=(4.8±1.0)×10(-3), and RD=(3.568±0.066)×10(-3). Allowing for CP violation, the measurement is performed separately for D0 and D0 mesons yielding AD=(-0.7±1.9)%, for the direct CP-violating asymmetry, and 0.75<|q/p|<1.24 at the 68.3% confidence level, for the parameter describing CP violation in mixing. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation.
The semileptonic CP asymmetry in B0-Bover ¯0 mixing, a(sl)(d), is measured in proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb-1, recorded by the LHCb experiment. ...Semileptonic B0 decays are reconstructed in the inclusive final states D-μ+ and D*-μ+, where the D- meson decays into the K+π-π- final state and the D*- meson into the Dover ¯0(→K+π-)π- final state. The asymmetry between the numbers of D(*)-μ+ and D(*)+μ- decays is measured as a function of the decay time of the B0 mesons. The CP asymmetry is measured to be a(sl)(d)=(-0.02±0.19±0.30)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of a(sl)(d) to date and is consistent with the prediction from the standard model.
A
bstract
A study of
D
+
π
−
,
D
0
π
+
and
D
∗+
π
−
final states is performed using
pp
collision data, corresponding to an integrated luminosity of 1.0 fb
−1
, collected at a centre-of-mass energy of ...7 TeV with the LHCb detector. The
D
1
(2420)
0
resonance is observed in the
D
∗+
π
−
final state and the
$ D_2^{*}\left( {2460} \right) $
resonance is observed in the
D
+
π
−
,
D
0
π
+
and
D
∗+
π
−
final states. For both resonances, their properties and spin-parity assignments are obtained. In addition, two natural parity and two unnatural parity resonances are observed in the mass region between 2500 and 2800 MeV. Further structures in the region around 3000 MeV are observed in all the
D
∗+
π
−
,
D
+
π
−
and
D
0
π
+
final states.
Top quark production in the forward region in proton-proton collisions is observed for the first time. The W+b final state with W→μν is reconstructed using muons with a transverse momentum, p_{T}, ...larger than 25 GeV in the pseudorapidity range 2.0<η<4.5. The b jets are required to have 50<p_{T}<100 GeV and 2.2<η<4.2, while the transverse component of the sum of the muon and b-jet momenta must satisfy p_{T}>20 GeV. The results are based on data corresponding to integrated luminosities of 1.0 and 2.0 fb^{-1} collected at center-of-mass energies of 7 and 8 TeV by LHCb. The inclusive top quark production cross sections in the fiducial region are σ(top)7 TeV=239±53(stat)±33(syst)±24(theory) fb,σ(top)8 TeV=289±43(stat)±40(syst)±29(theory) fb.These results, along with the observed differential yields and charge asymmetries, are in agreement with next-to-leading order standard model predictions.
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