2,002 research outputs found
Second Generation of 'Miranda Procedure' for CP Violation in Dalitz Studies of B (\& D \& \tau) Decays
The `Miranda Procedure' proposed for analyzing Dalitz plots for CP
asymmetries in charged B and D decays in a model-independent manner is extended
and refined. The complexity of CKM CP phenomenology through order
is needed in searches for New Dynamics (ND). Detailed analyses of three-body
final states other great advantages: (i) They give us more powerful tools for
deciding whether an observed CP asymmetry rep- resents the manifestation of ND
and its features. (ii) Many advantages can already be obtained by the `Miranda
Procedure' without construction of a detailed Dalitz plot de- scription. (iii)
One studies CP asymmetries independent of production asymmetries. We illustrate
the power of a second generation Miranda Procedure with examples with time
integrated rates for decays to final states as
trial runs with comments on .Comment: 29 pages, 7 figure
Search for CP violation in decays
A model-independent search for direct CP violation in the Cabibbo suppressed
decay in a sample of approximately 370,000 decays is
carried out. The data were collected by the LHCb experiment in 2010 and
correspond to an integrated luminosity of 35 pb. The normalized Dalitz
plot distributions for and are compared using four different
binning schemes that are sensitive to different manifestations of CP violation.
No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, 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
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Measurement of the lifetime
Using a data set corresponding to an integrated luminosity of ,
collected by the LHCb experiment in collisions at centre-of-mass energies
of 7 and 8 TeV, the effective lifetime in the
decay mode, , is measured to be ps. Assuming
conservation, corresponds to the lifetime of the light
mass eigenstate. This is the first measurement of the effective
lifetime in this decay mode.Comment: 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-2016-017.htm
Observation of excited Lambda_b0 baryons
Using pp collision data corresponding to 1.0 fb-1 integrated luminosity
collected by the LHCb detector, two narrow states are observed in the
Lambda_b0pi+pi- spectrum with masses 5911.97 +- 0.12(stat) +- 0.02(syst) +-
0.66(Lambda_b0 mass) MeV/c^2 and 5919.77 +- 0.08(stat) +- 0.02(syst) +-
0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 5.2 and
10.2 standard deviations, respectively. These states are interpreted as the
orbitally-excited Lambda_b0 baryons, Lambda_b*0(5912) and Lambda_b*0(5920).Comment: Replaced by version published in Phys. Rev. Lett, modified fit with
better mass resolution treatmen
Opposite-side flavour tagging of B mesons at the LHCb experiment
The calibration and performance of the oppositeside
flavour tagging algorithms used for the measurements
of time-dependent asymmetries at the LHCb experiment
are described. The algorithms have been developed using
simulated events and optimized and calibrated with
B
+ →J/ψK
+, B0 →J/ψK
∗0 and B0 →D
∗−
μ
+
νμ decay
modes with 0.37 fb−1 of data collected in pp collisions
at
√
s = 7 TeV during the 2011 physics run. The oppositeside
tagging power is determined in the B
+ → J/ψK
+
channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertainty
is statistical and the second is systematic
Observation of resonances consistent with pentaquark states in decays
Observations of exotic structures in the channel, that we refer to
as pentaquark-charmonium states, in decays are
presented. The data sample corresponds to an integrated luminosity of 3/fb
acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude
analysis is performed on the three-body final-state that reproduces the
two-body mass and angular distributions. To obtain a satisfactory fit of the
structures seen in the mass spectrum, it is necessary to include two
Breit-Wigner amplitudes that each describe a resonant state. The significance
of each of these resonances is more than 9 standard deviations. One has a mass
of MeV and a width of MeV, while the second
is narrower, with a mass of MeV and a width of MeV. The preferred assignments are of opposite parity, with one
state having spin 3/2 and the other 5/2.Comment: 48 pages, 18 figures including the supplementary material, v2 after
referee's comments, now 19 figure
Measurement of the mass and lifetime of the baryon
A proton-proton collision data sample, corresponding to an integrated
luminosity of 3 fb collected by LHCb at and 8 TeV, is used
to reconstruct , decays. Using the , decay mode for calibration, the lifetime ratio and absolute
lifetime of the baryon are measured to be \begin{align*}
\frac{\tau_{\Omega_b^-}}{\tau_{\Xi_b^-}} &= 1.11\pm0.16\pm0.03, \\
\tau_{\Omega_b^-} &= 1.78\pm0.26\pm0.05\pm0.06~{\rm ps}, \end{align*} where the
uncertainties are statistical, systematic and from the calibration mode (for
only). A measurement is also made of the mass difference,
, and the corresponding mass, which
yields \begin{align*} m_{\Omega_b^-}-m_{\Xi_b^-} &= 247.4\pm3.2\pm0.5~{\rm
MeV}/c^2, \\ m_{\Omega_b^-} &= 6045.1\pm3.2\pm 0.5\pm0.6~{\rm MeV}/c^2.
\end{align*} These results are consistent with previous measurements.Comment: 11 pages, 5 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-2016-008.htm
Strong constraints on the rare decays Bs -> mu+ mu- and B0 -> mu+ mu-
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-) mu+ mu-) < 1.0 (0.81) x 10^-9 at
95% (90%) confidence level.Comment: 2+6 pages; 4 figures; Accepted for publication in Physical Review
Letter
Measurement of the CP-violating phase phi_s in the decay Bs->J/psi phi
We present a measurement of the time-dependent CP-violating asymmetry in B_s
-> J/psi phi decays, using data collected with the LHCb detector at the LHC.
The decay time distribution of B_s -> J/psi phi is characterized by the decay
widths Gamma_H and Gamma_L of the heavy and light mass eigenstates of the
B_s-B_s-bar system and by a CP-violating phase phi_s. In a sample of about 8500
B_s -> J/psi phi events isolated from 0.37 fb^-1 of pp collisions at sqrt(s)=7
TeV we measure phi_s = 0.15 +/- 0.18 (stat) +/- 0.06 (syst) rad. We also find
an average B_s decay width Gamma_s == (Gamma_L + Gamma_H)/2 = 0.657 +/- 0.009
(stat) +/- 0.008 (syst) ps^-1 and a decay width difference Delta Gamma_s ==
Gamma_L - Gamma_H} = 0.123 +/- 0.029 (stat) +/- 0.011 (syst) ps^-1. Our
measurement is insensitive to the transformation (phi_s,DeltaGamma_s --> pi -
phi_s, - Delta Gamma_s.Comment: 9 pages, 3 figure
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