Performance of the LHCb RICH detector at the LHC Adinolfi, M.; Aglieri Rinella, G.; Albrecht, E. ...
The European physical journal. C, Particles and fields,
05/2013, Letnik:
73, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The LHCb experiment has been taking data at the Large Hadron Collider (LHC) at CERN since the end of 2009. One of its key detector components is the Ring-Imaging Cherenkov (RICH) system. This ...provides charged particle identification over a wide momentum range, from 2–100 GeV/
c
. The operation and control, software, and online monitoring of the RICH system are described. The particle identification performance is presented, as measured using data from the LHC. Excellent separation of hadronic particle types (
π
, K, p) is achieved.
The high data rates at the LHC necessitate the use of biasing selections already at the trigger level. Consequently, the correction of the biases induced by these selections becomes one of the main ...challenges for analyses. This paper presents the LHCb implementation of a data driven method for extracting such biases which entirely avoids uncertainties associated with detector simulation. Its novelty lies in the LHCb trigger which is implemented entirely in software, allowing its decisions to be reproduced in an exact manner offline. It is demonstrated that this method allows the control of selection biases to better than 0.1%, and that it greatly enhances the range of physics which can be performed by the LHCb experiment. The implications of trigger and software architectures on the long term viability of this method, in particular with respect to the reproducibility of trigger decisions when running the same code on different underlying hardware or compilers, is discussed.
In the Standard Model of particle physics, the strength of the couplings of the b quark to the u and c quarks, |Vub| and |Vcb|, are governed by the coupling of the quarks to the Higgs boson. Using ...data from the LHCb experiment at the Large Hadron Collider, the probability for the Λb0 baryon to decay into the p final state relative to the final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of |Vcb|, the first |Vub| measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of |Vub| using B meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states.
The production of the
η
c
(
1
S
)
state in proton-proton collisions is probed via its decay to the
p
p
¯
final state with the LHCb detector, in the rapidity range
2.0
<
y
<
4.5
and in the meson ...transverse-momentum range
p
T
>
6.5
GeV
/
c
. The cross-section for prompt production of
η
c
(
1
S
)
mesons relative to the prompt
J
/
ψ
cross-section is measured, for the first time, to be
σ
η
c
(
1
S
)
/
σ
J
/
ψ
=
1.74
±
0.29
±
0.28
±
0
.
18
B
at a centre-of-mass energy
s
=
7
TeV
using data corresponding to an integrated luminosity of 0.7 fb
-
1
, and
σ
η
c
(
1
S
)
/
σ
J
/
ψ
=
1.60
±
0.29
±
0.25
±
0
.
17
B
at
s
=
8
TeV
using 2.0 fb
-
1
. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the
η
c
(
1
S
)
and
J
/
ψ
decays to the
p
p
¯
final state. In addition, the inclusive branching fraction of
b
-hadron decays into
η
c
(
1
S
)
mesons is measured, for the first time, to be
B
(
b
→
η
c
X
)
=
(
4.88
±
0.64
±
0.29
±
0
.
67
B
)
×
10
-
3
, where the third uncertainty includes also the uncertainty on the
J
/
ψ
inclusive branching fraction from
b
-hadron decays. The difference between the
J
/
ψ
and
η
c
(
1
S
)
meson masses is determined to be
114.7
±
1.5
±
0.1
MeV
/
c
2
.
A
bstract
A study is presented of central exclusive production of Υ(
nS
) states, where the Υ(
nS
) resonances decay to the
μ
+
μ
−
final state, using
pp
collision data recorded by the LHCb ...experiment. The cross-section is measured in the rapidity range 2
< y
(Υ)
<
4
.
5 where the muons are reconstructed in the pseudorapidity range 2
< η
(
μ
±
)
<
4
.
5. The data sample corresponds to an integrated luminosity of 2.9 fb
−1
and was collected at centre-of-mass energies of 7 TeV and 8 TeV. The measured Υ(1
S
) and Υ(2
S
) production cross-sections are
σ
pp
→
p
Υ
1
S
p
=
9.0
±
2.1
±
1.7
p
b
and
σ
pp
→
p
Υ
2
S
p
=
1.3
±
0.8
±
0.3
p
b
,
where the first uncertainties are statistical and the second are systematic. The Υ(1
S
) crosssection is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive Υ(3
S
) production cross-section, including possible contamination from χ
b
(3
P
) → Υ(3
S
)γ decays.
A
bstract
Associated production of bottomonia and open charm hadrons in pp collisions at
s
=
7
and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb
−1
accumulated with ...the LHCb detector. The observation of five combinations, Y(1S)D
0
, Y(2S)D
0
, Y(1S)D
+
, Y(2S)D
+
and Y(1S)D
s
+
, is reported. Production crosssections are measured for Y(1S)D
0
and Y(1S)D
+
pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism.
The angular distribution and differential branching fraction of the decay $B^{0} \to K^{*0} \mu^{+}\mu^{-}$ are studied using a data sample, collected by the LHCb experiment in $pp$ collisions at ...$\sqrt{s}=7\,{\rm TeV}$, corresponding to an integrated luminosity of $1.0\,{\rm fb}^{-1}$. 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 $q_{0}^{2} = 4.9 \pm 0.9 \,{\rm GeV}^{2}/c^{4}$, where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.
A
bstract
The production of
J/ψ
mesons in proton-proton collisions at a centre-of-mass energy of
s
=
13
TeV is studied with the LHCb detector. Cross-section measurements are performed as a function ...of the transverse momentum
p
T
and the rapidity
y
of the
J/ψ
meson in the region
p
T
<
14 GeV/
c
and 2
.
0
< y <
4
.
5, for both prompt
J/ψ
mesons and
J/ψ
mesons from
b
-hadron decays. The production cross-sections integrated over the kinematic coverage are 15
.
30 ± 0
.
03 ± 0
.
86 μb for prompt
J/ψ
and 2
.
34 ± 0
.
01 ± 0
.
13 μb for
J/ψ
from
b
-hadron decays, assuming zero polarization of the
J/
ψ meson. The first uncertainties are statistical and the second systematic. The cross-section reported for
J/ψ
mesons from
b
-hadron decays is used to extrapolate to a total
b
b
¯
cross-section. The ratios of the cross-sections with respect to
s
=
8
TeV are also determined.
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 5911.95 +- ...0.12(stat) +- 0.03(syst) +- 0.66(Lambda_b0 mass) MeV/c^2 and 5919.76 +- 0.07(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 4.9 and 10.1 standard deviations, respectively. These states are interpreted as the orbitally-excited Lambda_b0 baryons, Lambda_b*0(5912) and Lambda_b*0(5920).
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