LHCb reoptimized detector design and performance: Technical Design Report

The LHCb experiment has been conceived to study CP violation and other rare phenomena in B meson decays with very high precision. This should provide a profound understanding of quark flavour physics in the framework of the Standard Model, and may reveal a sign of the physics beyond. In order to achieve these goals, the LHCb detector must have a high track reconstruction efficiency, π– K separation capability from a few to ∼100 GeV/c, very good proper-time resolution of ∼ 40 fs and high trigger efficiencies, not only for final states including leptons but also for those with hadrons alone. The detector described in the Technical Proposal (TP) [1], approved in September 1998, was designed to fulfil those requirements. This document describes a reoptimization of the detector, that has been made to reduce the material budget and to improve the trigger performance. At the time of the TP the material budget up to the second Ring Imaging Cherenkov detector (RICH2) was 40% of X0 (10% of λI), where X0 (λI) is the radiation (nuclear interaction) length. This increased to 60% (20%) by the time the Outer Tracker Technical Design Report (TDR) [2] was submitted in September 2001, due to various technological constraints. Additional material deteriorates the detection capability of electrons and photons, increases the multiple scattering of charged particles, and increases occupancies of the tracking stations. With a larger fraction of nuclear interaction length, more kaons and pions interact before traversing the complete tracking system. The number of reconstructed B mesons therefore decreases, even if the efficiency of the tracking algorithm is maintained high for those tracks that do traverse the full spectrometer. This leads to a noticeable loss in the number of reconstructed B mesons from many-body final states. For example, one of the most promising CP violation measurements, from Bs → DsK decays, requires five charged tracks (including one for tagging) to be reconstructed. For these reasons, an effort has been made to reduce the material budget back to the level at the time of the TP. The trigger is one of the biggest challenges of the LHCb experiment1. It is designed to distinguish minimum-bias events from events containing B mesons through the presence of particles with a large transverse momentum (pT) and the existence of secondary vertices. Events are first triggered by requiring at least one lepton or hadron with a pT exceeding 1 to 3 GeV/c (Level-0) reducing the event rate to 1MHz. It was realised that the robustness and efficiency of the second trigger level (Level-1) could be significantly improved by not only using information from the Vertex Locator (VELO), as done in the TP, but also adding pT information to tracks with a large impact parameter. This can be achieved by associating the high-pT calorimeter clusters and muons obtained at Level-0 to the tracks found in the VELO [3]. A complementary approach that is more efficient for hadrons is to get a rough pT estimate from the tracking. This requires the introduction of a small amount of magnetic field in the region of RICH1. The design of RICH 1 then has to be modified in order to protect its photon detectors from the field

Connections in the L0 Calorimeter trigger

This note summarizes the specification of the interfaces and connections between various components of the L0 Calorimeter system

Measurement of the Nuclear Modification Factor and Prompt Charged Particle Production in p−Pbp-Pb and pppp Collisions at sNN\sqrt {s_{NN}}=5 TeV

International audienceThe production of prompt charged particles in proton-lead collisions and in proton-proton collisions at the nucleon-nucleon center-of-mass energy sNN=5  TeV is studied at LHCb as a function of pseudorapidity (η) and transverse momentum (pT) with respect to the proton beam direction. The nuclear modification factor for charged particles is determined as a function of η between -4.8<η<-2.5 (backward region) and 2.0<η<4.8 (forward region), and pT between 0.2<pT<8.0  GeV/c. The results show a suppression of charged particle production in proton-lead collisions relative to proton-proton collisions in the forward region and an enhancement in the backward region for pT larger than 1.5  GeV/c. This measurement constrains nuclear PDFs and saturation models at previously unexplored values of the parton momentum fraction down to 10-6

Search for the lepton-flavour violating decays B0→K∗0μ±e∓B^0 \to K^{*0} \mu^\pm e^\mp and Bs0→ϕμ±e∓B_s^0 \to \phi \mu^\pm e^\mp

A search for the lepton-flavour violating decays $B^0 \to K^{*0} \mu^\pm e^\mp$ and $B_s^0 \to \phi \mu^\pm e^\mp$ is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$. No significant signals are observed and upper limits of \begin{align} {\cal B}( B^0 \to K^{*0} \mu^+ e^- ) &< \phantom{1}5.7\times 10^{-9}~(6.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^- e^+ ) &< \phantom{1}6.8\times 10^{-9}~(7.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^\pm e^\mp ) &< 10.1\times 10^{-9}~(11.7\times 10^{-9}),\newline {\cal B}( B_s^0 \to \phi \mu^\pm e^\mp ) &< 16.0\times 10^{-9}~(19.8\times 10^{-9}) \end{align} are set at $90\%~(95\%)$ confidence level. These results constitute the world's most stringent limits to date, with the limit on the decay $B_s^0 \to \phi \mu^\pm e^\mp$ the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.A search for the lepton-flavour violating decays B$^{0}$ → K$^{*0}$μ$^{±}$e$^{∓}$ and ${B}_s^0$→ ϕμ$^{±}$e$^{∓}$ is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of 9 fb$^{−1}$. No significant signals are observed and upper limits of${\displaystyle \begin{array}{c}\mathcal{B}\left({B}^0\to {K}^{\ast 0}{\mu}^{+}{e}^{-}\right)<5.7\times {10}^{-9}\left(6.9\times {10}^{-9}\right),\\ {}\mathcal{B}\left({B}^0\to {K}^{\ast 0}{\mu}^{-}{e}^{+}\right)<6.8\times {10}^{-9}\left(7.9\times {10}^{-9}\right),\\ {}\mathcal{B}\left({B}^0\to {K}^{\ast 0}{\mu}^{\pm }{e}^{\mp}\right)<10.1\times {10}^{-9}\left(11.7\times {10}^{-9}\right),\\ {}\mathcal{B}\left({B}_s^0\to \phi {\mu}^{\pm }{e}^{\mp}\right)<16.0\times {10}^{-9}\left(19.8\times {10}^{-9}\right)\end{array}}$are set at 90% (95%) confidence level. These results constitute the world’s most stringent limits to date, with the limit on the decay ${B}_s^0$→ ϕμ$^{±}$e$^{∓}$ the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.[graphic not available: see fulltext]A search for the lepton-flavour violating decays $B^0 \to K^{*0} \mu^\pm e^\mp$ and $B_s^0 \to \phi \mu^\pm e^\mp$ is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$. No significant signals are observed and upper limits of \begin{align} {\cal B}( B^0 \to K^{*0} \mu^+ e^- ) &< \phantom{1}5.7\times 10^{-9}~(6.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^- e^+ ) &< \phantom{1}6.8\times 10^{-9}~(7.9\times 10^{-9}),\newline {\cal B}( B^0 \to K^{*0} \mu^\pm e^\mp ) &< 10.1\times 10^{-9}~(11.7\times 10^{-9}),\newline {\cal B}( B_s^0 \to \phi \mu^\pm e^\mp ) &< 16.0\times 10^{-9}~(19.8\times 10^{-9}) \end{align} are set at $90\%~(95\%)$ confidence level. These results constitute the world's most stringent limits to date, with the limit on the decay $B_s^0 \to \phi \mu^\pm e^\mp$ the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

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