60 research outputs found
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A Search for Dark Higgs Bosons
Recent astrophysical and terrestrial experiments have motivated the proposal
of a dark sector with GeV-scale gauge boson force carriers and new Higgs
bosons. We present a search for a dark Higgs boson using 516 fb-1 of data
collected with the BABAR detector. We do not observe a significant signal and
we set 90% confidence level upper limits on the product of the Standard
Model-dark sector mixing angle and the dark sector coupling constant.Comment: 7 pages, 5 postscript figures, published version with improved plots
for b/w printin
Measurement of D s <sup>±</sup> production asymmetry in pp collisions at √s=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)0→J/ψpp¯ decays and precision measurements of the B(s)0 masses
The first observation of the decays
B
0
(
s
)
→
J
/
ψ
p
¯
p
is reported, using proton-proton collision data corresponding to an integrated luminosity of
5.2
fb
−
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
→
J
/
ψ
p
¯
p
)
=
[
4.51
±
0.40
(
stat
)
±
0.44
(
syst
)
]
×
10
−
7
,
B
(
B
0
s
→
J
/
ψ
p
¯
p
)
=
[
3.58
±
0.19
(
stat
)
±
0.39
(
syst
)
]
×
10
−
6
. For the
B
0
s
meson, the result is much higher than the expected value of
O
(
10
−
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
)
MeV
and the
B
0
s
mass as
5366.85
±
0.19
(
stat
)
±
0.13
(
syst
)
MeV
Observation of the decay Λ <sub>b</sub> <sup>0</sup> → ψ(2S)pπ<sup>−</sup>
International audienceThe Cabibbo-suppressed decay Λ → ψ(2S)pπ 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 ψ(2S) mesons are reconstructed in the μμ final state. The branching fraction with respect to that of the Λ → ψ(2S)pK decay mode is measured to b
Search for CP violation in Λb0→pK− and Λb0→pπ− decays
A search for CP violation in Λb0→pK− and Λb0→pπ− decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0fb−1. The CP -violating asymmetries are measured to be ACPpK−=−0.020±0.013±0.019 and ACPpπ−=−0.035±0.017±0.020, and their difference ACPpK−−ACPpπ−=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 B0→ηc(1S)K+π- 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)π- 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 B0→ηc(1S)K+π- branching fraction is performed and gives B(B0→ηc(1S)K+π-)=(5.73±0.24±0.13±0.66)×10-4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions
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
→
μ
þ
μ
−
decays and a data sample corresponding
to an integrated luminosity of
1
.
6
fb
−
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
ð
A
0
Þ
<
350
MeV. No evidence for a signal is found, and 90% confidence
level exclusion limits are placed on the
γ
–
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
ð
A
0
Þ
<
70
GeV, and are
comparable to the best existing limits for
m
ð
A
0
Þ
<
0
.
5
GeV. The search for long-lived dark photons is the
first to achieve sensitivity using a displaced-vertex signature
Amplitude analysis of the B0 (s)! K0K0 decays and measurement of the branching fraction of the B0! K0K0 decay
The and decays are studied using proton-proton collision data
corresponding to an integrated luminosity of 3fb. An untagged and
time-integrated amplitude analysis of
decays in two-body invariant mass regions of 150 MeV around the
mass is performed. A stronger longitudinal polarisation fraction in the decay, , is observed as compared to in the decay. The ratio of branching fractions of the two decays
is measured and used to determine .Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2019-004.html (LHCb
public pages
Amplitude analysis of B-s(0) -> K-S(0) K-+/-pi(-/+) decays
The first untagged decay-time-integrated amplitude analysis of decays is performed using a
sample corresponding to fb of collision data recorded with
the LHCb detector during 2011 and 2012. The data are described with an
amplitude model that contains contributions from the intermediate resonances
, and , and their
charge conjugates. Measurements of the branching fractions of the decay modes
and are in agreement with, and
more precise than, previous results. The decays and are observed for the first time, each with
significance over 10 standard deviations.Comment: 27 pages, 14 figures. All figures and tables, along with any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2018-045.htm
First measurement of the -violating phase in decays
A flavour-tagged decay-time-dependent amplitude analysis of decays is presented in the mass range from 750 to 1600 MeV. The analysis uses collision data collected with the LHCb detector at centre-of-mass energies of and TeV, corresponding to an integrated luminosity of fb. Several quasi-two-body decay modes are considered, corresponding to combinations with spin 0, 1 and 2, which are dominated by the and , the and the resonances, respectively. The longitudinal polarisation fraction for the decay is measured as , where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced -violating phase, , in transitions is performed, yielding a value of (stat) (syst) rad
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