2,331 research outputs found
b-hadrons lifetime measurements using exclusive b -> J/psi(mu(+) mu(-)) X decays at LHCb
In the proceeding are reported precision measurement of differ ent b-hadrons lifetimes in the exclusive decays B+ -> J / psi K+ , B-0 -> j / psi K-*0 B-s(0) -> J / psi A, using 1 fb(-1) of data collected in 2011 with the LHCb detector at a centre-of-mass energy of 7 TeV
On the impact of the Migdal effect in reactor CENS experiments
The search for coherent elastic neutrino nucleus scattering (CENS) using
reactor antineutrinos represents a formidable experimental challenge, recently
boosted by the observation of such a process at the Dresden-II reactor site
using a germanium detector. This observation relies on an unexpected
enhancement at low energies of the measured quenching factor with respect to
the theoretical Lindhard model prediction, which implies an extra observable
ionization signal produced after the nuclear recoil. A possible explanation for
this additional contribution could be provided by the so-called Migdal effect,
which however has never been observed. Here, we study in detail the impact of
the Migdal contribution to the standard CENS signal calculated with the
Lindhard quenching factor, finding that the former is completely negligible for
observed energies below where the signal is
detectable, and thus unable to provide any contribution to CENS searches
in this energy regime. To this purpose, we compare different formalisms used to
describe the Migdal effect that intriguingly show a perfect agreement, making
our findings robust.Comment: 5 pages, 2 figure
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
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
Differential branching fraction and angular analysis of the decay B0→K∗0μ+μ−
The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
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