A first alignment of the LHCb Vertex Locator has been obtained from beam induced tracks at the LHC. A 450
GeV/
c protons were collided on a beam absorber during the LHC synchronisation tests of the ...anti-clockwise beam in August and September 2008. The resulting particle tracks have been reconstructed by the Vertex Locator. This was the first full reconstruction of tracks induced by the LHC beam. The quality of the data obtained is discussed. A total of 2200 tracks were reconstructed from the full data sample, and a first spatial alignment was obtained. The detector is aligned to an accuracy of
5
μ
m
in the sensor plane. The results confirm that all detector modules have not been displaced from their surveyed positions by more than
10
μ
m
.
The B−→D+K−π− decay is observed in a data sample corresponding to 3.0 fb−1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. Its branching fraction is measured to be ...B(B−→D+K−π−)=(7.92±0.23±0.24±0.42)×10−5 where the uncertainties are statistical, systematic and from the branching fraction of the normalisation channel B−→D+π−π−, respectively. An amplitude analysis of the resonant structure of the B−→D+K−π− decay is used to measure the contributions from quasi-two-body B−→D∗0(2400)0K−, B−→D∗2(2460)0K−, and B−→D∗J(2760)0K− decays, as well as from nonresonant sources. The D∗J(2760)0 resonance is determined to have spin~1.
The production of
mesons in proton–proton collisions at
is studied with the LHCb detector at the LHC. The differential cross-section for prompt
production is measured as a function of the
transverse ...momentum p
T
and rapidity
y
in the fiducial region
and
y
∈2.0;4.5. The differential cross-section and fraction of
from
b
-hadron decays are also measured in the same p
T
and
y
ranges. The analysis is based on a data sample corresponding to an integrated luminosity of 5.2 pb
−1
. The measured cross-sections integrated over the fiducial region are
for prompt
production and
for
from
b
-hadron decays, where the first uncertainty is statistical and the second systematic. The prompt
production cross-section is obtained assuming no
polarisation and the third error indicates the acceptance uncertainty due to this assumption.
First LHC beam induced tracks reconstructed in the LHCb VELO Parkes, C.; Borghi, S.; Bates, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2009, Letnik:
604, Številka:
1
Journal Article
Recenzirano
The Vertex Locator of the LHCb experiment has been used to fully reconstruct beam induced tracks at the LHC. A beam of protons was collided with a beam absorber during the LHC synchronisation test of ...the anti-clockwise beam on the weekend 22nd–24th August 2008. The resulting particles have been observed by the Vertex Locator. The LHCb Vertex Locator is a silicon micro-strip detector containing 21 planes of modules. Tracks were observed passing through up to 19 modules (38 silicon sensors). A total of over 700 tracks were reconstructed, and are being used to study the calibration and alignment of the detector.
A baryonic decay of the B + c meson, B + c → J / ψ p ¯ p π + , is observed for the first time, with a significance of 7.3 standard deviations, in p p collision data collected with the LHCb detector ...and corresponding to an integrated luminosity of 3.0 fb − 1 taken at center-of-mass energies of 7 and 8 TeV. With the B + c → J / ψ π + decay as the normalization channel, the ratio of branching fractions is measured to be B ( B + c → J / ψ p ¯ p π + ) / B ( B + c → J / ψ π + ) = 0.14 3 + 0.039 − 0.034 ( stat ) ± 0.013 ( syst ) . The mass of the B + c meson is determined as M ( B + c ) = 6274.0 ± 1.8 ( stat ) ± 0.4 ( syst ) MeV / c 2 , using the B + c → J / ψ p ¯ p π + channel.
The associated production of a W boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data ...corresponding to integrated luminosities of 1.0 and 2.0fb−1 collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The W bosons are reconstructed using the W→μν decay and muons with a transverse momentum, pT, larger than 20 GeV in the pseudorapidity range 2.0<η<4.5. The partons are reconstructed as jets with pT>20 GeV and 2.2<η<4.2. The sum of the muon and jet momenta must satisfy pT>20 GeV. The fraction of W+jet events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the W+b and W+c production cross-sections. The ratio of the W+jet to Z+jet production cross-sections is also measured using the Z→μμ decay. All results are in agreement with Standard Model predictions.
The LHCb measurement of the lifetime ratio of the Λb0 baryon to the B¯0 meson is updated using data corresponding to an integrated luminosity of 3.0 fb−1 collected using 7 and 8 TeV centre-of-mass ...energy pp collisions at the LHC. The decay modes used are Λb0→J/ψpK− and B¯0→J/ψπ+K−, where the π+K− mass is consistent with that of the K¯⁎0(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974±0.006±0.004, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion. Using the current world average of the B¯0 lifetime, the Λb0 lifetime is found to be 1.479±0.009±0.010 ps.
A
bstract
The first observation of
Z
boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of
s
N
N
= 5 TeV is presented. The data sample corresponds to an ...integrated luminosity of 1
.
6 nb
−1
collected with the LHCb detector. The
Z
candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above 20 GeV
/
c. The invariant dimuon mass is restricted to the range 60 − 120 GeV
/
c. The
Z
production cross-section is measured to be
σ
Z
→
μ
+
μ
−
fwd
=
13.5
−
4.0
+
5.4
stat
.
±
1.2
syst
.
nb
in the direction of the proton beam and
σ
Z
→
μ
+
μ
−
bwd
=
10.7
−
5.1
+
8.4
stat
.
±
1.0
syst
.
nb
in the direction of the lead beam, where the first uncertainty is statistical and the second systematic.
PDF
