During 2011 the LHCb experiment at CERN collected 1.0 fb
−1
of
pp
collisions. Due to the large heavy quark production cross-sections, these data provide unprecedented samples of heavy flavoured ...hadrons. The first results from LHCb have made a significant impact on the flavour physics landscape and have definitively proved the concept of a dedicated experiment in the forward region at a hadron collider. This document discusses the implications of these first measurements on classes of extensions to the Standard Model, bearing in mind the interplay with the results of searches for on-shell production of new particles at ATLAS and CMS. The physics potential of an upgrade to the LHCb detector, which would allow an order of magnitude more data to be collected, is emphasised.
The calibration and performance of the opposite-side 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
+
,
B
0
→
J
/
ψK
∗0
and
B
0
→
D
∗−
μ
+
ν
μ
decay modes with 0.37 fb
−1
of data collected in
pp
collisions at
during the 2011 physics run. The opposite-side 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.
A
bstract
The angular distribution and differential branching fraction of the decay
B
+
→
K
+
μ
+
μ
−
are studied with a dataset corresponding to 1.0fb
−1
of integrated luminosity, collected by the ...LHCb experiment. The angular distribution is measured in bins of dimuon invariant mass squared and found to be consistent with Standard Model expectations. Integrating the differential branching fraction over the full dimuon invariant mass range yields a total branching fraction of
(
B
+
→
K
+
μ
+
μ
−
) = (4
.
36
±
0
.
15
±
0
.
18)
×
10
−7
. These measurements are the most precise to date of the
B
+
→
K
+
μ
+
μ
−
decay.
The relative production rate of $B^{0}_{s}$ and $B^{0}$ mesons is determined with the hadronic decays $B^{0}_{s} \rightarrow D^{-}_{s}\pi^{+}$ and $B^0 \rightarrow D^{-}K^{+}$. The measurement uses ...data corresponding to 1.0 fb$^{-1}$ of $pp$ collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV recorded in the forward region with the LHCb experiment. The ratio of production rates, $f_{s}/f_{d}$, is measured to be $0.238 \pm 0.004 \pm 0.015 \pm 0.021 $, where the first uncertainty is statistical, the second systematic, and the third theoretical. This is combined with a previous LHCb measurement to obtain $f_{s}/f_{d} = 0.256 \pm 0.020$. The dependence of $f_{s}/f_{d}$ on the transverse momentum and pseudorapidity of the $B$ meson is determined using the decays $B^{0}_{s} \rightarrow D^{-}_{s}\pi^{+}$ and $B^{0} \rightarrow D^{-}\pi^{+}$. There is evidence for a decrease with increasing transverse momentum, whereas the ratio remains constant as a function of pseudorapidity. In addition, the ratio of branching fractions of the decays $B^{0} \rightarrow D^{-}K^{+}$ and $B^{0} \rightarrow D^{-}\pi^{+}$ is measured to be $0.0822 \pm 0.0011 (\textrm{stat}) \pm 0.0025 (\textrm{syst})$.
A
bstract
Based on data corresponding to an integrated luminosity of 0.37 fb
−1
collected by the LHCb experiment in 2011, the following ratios of branching fractions are measured:
where the first ...uncertainties are statistical and the second systematic. Using the current world average of
and the ratio of the strange to light neutral
B
meson production
f
s
/
f
d
measured by LHCb, we obtain:
The measurements of
,
and
are the most precise to date. The decay mode
is observed for the first time with a significance of more than 5
σ
.
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