67 research outputs found
Measurement of D s <sup>±</sup> production asymmetry in pp collisions at âs=7 and 8 TeV
The inclusive production asymmetry is measured in collisions
collected by the LHCb experiment at centre-of-mass energies of
and 8 TeV. Promptly produced mesons are used, which decay as
, with . The measurement is
performed in bins of transverse momentum, , and rapidity, ,
covering the range GeV and . No kinematic
dependence is observed. Evidence of nonzero production asymmetry is
found with a significance of 3.3 standard deviations.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2018-010.htm
Observation of B(s)0âJ/ÏppÂŻ decays and precision measurements of the B(s)0 masses
The first observation of the decays
B
0
(
s
)
â
J
/
Ï
p
ÂŻ
p
is reported, using proton-proton collision data corresponding to an integrated luminosity of
5.2
â
â
fb
â
1
, collected with the LHCb detector. These decays are suppressed due to limited available phase space, as well as due to Okubo-Zweig-Iizuka or Cabibbo suppression. The measured branching fractions are
B
(
B
0
â
J
/
Ï
p
ÂŻ
p
)
=
[
4.51
±
0.40
(
stat
)
±
0.44
(
syst
)
]
Ă
10
â
7
,
B
(
B
0
s
â
J
/
Ï
p
ÂŻ
p
)
=
[
3.58
±
0.19
(
stat
)
±
0.39
(
syst
)
]
Ă
10
â
6
. For the
B
0
s
meson, the result is much higher than the expected value of
O
(
10
â
9
)
. The small available phase space in these decays also allows for the most precise single measurement of both the
B
0
mass as
5279.74
±
0.30
(
stat
)
±
0.10
(
syst
)
â
â
MeV
and the
B
0
s
mass as
5366.85
±
0.19
(
stat
)
±
0.13
(
syst
)
â
â
MeV
Observation of the decay Î <sub>b</sub> <sup>0</sup> âââÏ(2S)pÏ<sup>â</sup>
International audienceThe Cabibbo-suppressed decay Î âââÏ(2S)pÏ is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb of integrated luminosity at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The Ï(2S) mesons are reconstructed in the ΌΌ final state. The branching fraction with respect to that of the Î âââÏ(2S)pK decay mode is measured to b
Measurement of the B_{s}^{0}âÎŒ^{+}ÎŒ^{-} Branching Fraction and Effective Lifetime and Search for B^{0}âÎŒ^{+}ÎŒ^{-} Decays.
A search for the rare decays B_{s}^{0}âÎŒ^{+}ÎŒ^{-} and B^{0}âÎŒ^{+}ÎŒ^{-} is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4ââfb^{-1}. An excess of B_{s}^{0}âÎŒ^{+}ÎŒ^{-} decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B_{s}^{0}âÎŒ^{+}ÎŒ^{-})=(3.0±0.6_{-0.2}^{+0.3})Ă10^{-9}, where the first uncertainty is statistical and the second systematic. The first measurement of the B_{s}^{0}âÎŒ^{+}ÎŒ^{-} effective lifetime, Ï(B_{s}^{0}âÎŒ^{+}ÎŒ^{-})=2.04±0.44±0.05ââps, is reported. No significant excess of B^{0}âÎŒ^{+}ÎŒ^{-} decays is found, and a 95% confidence level upper limit, B(B^{0}âÎŒ^{+}ÎŒ^{-})<3.4Ă10^{-10}, is determined. All results are in agreement with the standard model expectations
Search for CP violation in Îb0âpKâ and Îb0âpÏâ decays
A search for CP violation in Îb0âpKâ and Îb0âpÏâ decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0fbâ1. The CP -violating asymmetries are measured to be ACPpKâ=â0.020±0.013±0.019 and ACPpÏâ=â0.035±0.017±0.020, and their difference ACPpKââACPpÏâ=0.014±0.022±0.010, where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date
Evidence for an nc(1S)ff- resonance in B0 yc(1S)K+ decays
A Dalitz plot analysis of B0âηc(1S)K+Ï- decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of s=7,8 and 13TeV , corresponding to a total integrated luminosity of 4.7fb-1 . A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1S)Ï- resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096±20-22+18MeV and 152±58-35+60MeV , respectively. The spin-parity assignments JP=0+ and JP=1- are both consistent with the data. In addition, the first measurement of the B0âηc(1S)K+Ï- branching fraction is performed and gives B(B0âηc(1S)K+Ï-)=(5.73±0.24±0.13±0.66)Ă10-4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions
Measurement of the B0sâÎŒ+ÎŒâ Branching Fraction and Effective Lifetime and Search for B0âÎŒ+ÎŒâ Decays
See paper for full list of authors - All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2017-001.html - Submitted to Phys. Rev. Lett.International audienceA search for the rare decays B0sâÎŒ+ÎŒâ and B0âÎŒ+ÎŒâ is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fbâ1. An excess of B0sâÎŒ+ÎŒâ decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B0sâÎŒ+ÎŒâ)=(3.0±0.6+0.3â0.2)Ă10â9, where the first uncertainty is statistical and the second systematic. The first measurement of the B0sâÎŒ+ÎŒâ effective lifetime, Ï(B0sâÎŒ+ÎŒâ)=2.04±0.44±0.05 ps, is reported. No significant excess of B0âÎŒ+ÎŒâ decays is found and a 95 % confidence level upper limit, B(B0âÎŒ+ÎŒâ)<3.4Ă10â10, is determined. All results are in agreement with the Standard Model expectations
Search for dark photons produced in 13 TeV collisions
Searches are performed for both promptlike and long-lived dark photons,
A
0
, produced in proton-proton
collisions at a center-of-mass energy of 13 TeV, using
A
0
â
Ό
ĂŸ
Ό
â
decays and a data sample corresponding
to an integrated luminosity of
1
.
6
fb
â
1
collected with the LHCb detector. The promptlike
A
0
search covers
the mass range from near the dimuon threshold up to 70 GeV, while the long-lived
A
0
search is restricted to
the low-mass region
214
<m
Ă°
A
0
Ă
<
350
MeV. No evidence for a signal is found, and 90% confidence
level exclusion limits are placed on the
Îł
â
A
0
kinetic-mixing strength. The constraints placed on promptlike
dark photons are the most stringent to date for the mass range
10
.
6
<m
Ă°
A
0
Ă
<
70
GeV, and are
comparable to the best existing limits for
m
Ă°
A
0
Ă
<
0
.
5
GeV. The search for long-lived dark photons is the
first to achieve sensitivity using a displaced-vertex signature
Observation of Five New Narrow Omega(0)(c) States Decaying to Xi K-+(c)-
The mass spectrum is studied with a sample of collision
data corresponding to an integrated luminosity of 3.3 fb, collected by
the LHCb experiment. The is reconstructed in the decay mode . Five new, narrow excited states are observed: the
, , , ,
and . Measurements of their masses and widths are reported.Comment: 14 pages, 3 figures. All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2017-002.htm
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