2,962 research outputs found
Absolute luminosity measurements with the LHCb detector at the LHC
No full textAbsolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. Using data taken in 2010, LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic ''van der Meer scan'' method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overal precision of 3.5% in the absolute luminosity determination is reached. The techniques used to transport the absolute luminosity calibration to the full 2010 data-taking period are presented
Observation of Z production in proton-lead collisions at LHCb
No full textThe first observation of Z boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of √sNN = 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
σZ→μ+μ−(fwd)=13.5+5.4−4.0(stat.)±1.2(syst.) nb
in the direction of the proton beam and
σZ→μ+μ−(bwd)=10.7+8.4−5.1(stat.)±1.0(syst.) nb
in the direction of the lead beam, where the first uncertainty is statistical and the second systematic
LHCb detector performance
No full textThe LHCb detector is a forward spectrometer at the Large Hadron Collider (LHC) at
CERN. The experiment is designed for precision measurements of CP violation and rare
decays of beauty and charm hadrons. In this paper the performance of the various LHCb
sub-detectors and the trigger system are described, using data taken from 2010 to 2012.
It is shown that the design criteria of the experiment have been met. The excellent
performance of the detector has allowed the LHCb collaboration to publish a wide range
of physics results, demonstrating LHCb’s unique role, both as a heavy flavour experiment
and as a general purpose detector in the forward region
LHCb detector performance
No full textThe LHCb detector is a forward spectrometer at the Large Hadron Collider (LHC) at
CERN. The experiment is designed for precision measurements of CP violation and rare
decays of beauty and charm hadrons. In this paper the performance of the various LHCb
sub-detectors and the trigger system are described, using data taken from 2010 to 2012.
It is shown that the design criteria of the experiment have been met. The excellent
performance of the detector has allowed the LHCb collaboration to publish a wide range
of physics results, demonstrating LHCb’s unique role, both as a heavy flavour experiment
and as a general purpose detector in the forward region
Implications of LHCb measurements and future prospects
No full textDuring 2011 the LHCb experiment at CERN collected 1.0 fb−1 of s√=7~TeV 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
Radiation damage in the LHCb vertex locator
No full textThe LHCb Vertex Locator (VELO) is a silicon strip detector designed to reconstruct charged particle trajectories and vertices produced at the LHCb interaction region. During the first two years of data collection, the 84 VELO sensors have been exposed to a range of fluences up to a maximum value of approximately 45 × 1012 1 MeV neutron equivalent (1 MeV neq). At the operational sensor temperature of approximately −7 °C, the average rate of sensor current increase is 18 μA per fb−1, in excellent agreement with predictions. The silicon effective bandgap has been determined using current versus temperature scan data after irradiation, with an average value of Eg = 1.16±0.03±0.04 eV obtained. The first observation of n+-on-n sensor type inversion at the LHC has been made, occurring at a fluence of around 15 × 1012 of 1 MeV neq. The only n+-on-p sensors in use at the LHC have also been studied. With an initial fluence of approximately 3 × 1012 1 MeV neq, a decrease in the Effective Depletion Voltage (EDV) of around 25 V is observed. Following this initial decrease, the EDV increases at a comparable rate to the type inverted n+-on-n type sensors, with rates of (1.43±0.16) × 10−12 V/ 1 MeV neq and (1.35±0.25) × 10−12 V/ 1 MeV neq measured for n+-on-p and n+-on-n type sensors, respectively. A reduction in the charge collection efficiency due to an unexpected effect involving the second metal layer readout lines is observed
Updated measurements of exclusive J/ψ and ψ(2S) production cross-sections in pp collisions at TeV
No full textThe differential cross-section as a function of rapidity has been measured for the exclusive production of J/ψ and ψ(2S) mesons in proton–proton collisions at TeV, using data collected by the LHCb experiment, corresponding to an integrated luminosity of 930 pb−1. The cross-sections times branching fractions to two muons having pseudorapidities between 2.0 and 4.5 are measured to be
where the first uncertainty is statistical and the second is systematic. The measurements agree with next-to-leading order QCD predictions as well as with models that include saturation effects
Measurement of the D+/- production asymmetry in 7 TeV pp collisions
No full textThe asymmetry in the production cross-section \sigma of D+/- mesons, A_P = (\sigma(D+) - \sigma(D-))/(\sigma(D+) + \sigma(D-)), is measured in bins of pseudorapidity \eta and transverse momentum p_T within the acceptance of the LHCb detector. The result is obtained with a sample of D+ -> K_S pi+ decays corresponding to an integrated luminosity of 1.0 fb^-1, collected in pp collisions at a centre of mass energy of 7 TeV at the Large Hadron Collider. When integrated over the kinematic range 2.0 K_S pi+ decay is negligible. No significant dependence on \eta or p_T is observed
Exclusive J/ψ and ψ(2S) production inppcollisions at √<span style="text-decoration:overline">s</span>=7 TeV
No full textExclusive J/ψ and ψ (2S) vector meson production has been observed in the
dimuon channel using the LHCb detector. The cross-section times branching
fractions to two muons with pseudorapidities between 2.0 and 4.5 are measured
to be
σpp→J/ψ (→μ
+μ
−)
(2.0 < ημ
± < 4.5) = 307±21±36 pb,
σpp→ψ (2S)(→μ
+μ
−)
(2.0 < ημ
± < 4.5) = 7.8±1.3±1.0 pb,
where the first uncertainties are statistical and the second are systematic.
The measurements are found to be in good agreement with results from
previous experiments and theoretical predictions. The J/ψ photoproduction
cross-section has been measured as a function of the photon-proton centre-ofmass energy. The results are consistent with measurements obtained at HERA
and confirm a similar power law behaviour for the photoproduction crosssection
LHCb: ECAL PID Enhancement
No full textThe Technical Design Report describes the enhancements of the ECAL and RICH detectors of LHCb that are proposed for implementation during Long Shutdown 3 of the LHC. For the ECAL, a replacement of the innermost modules, which will be affected by radiation damage incurred by the end of Run 3
- …
