The LHCb RICH upgrade for the high luminosity LHC era Wotton, S.A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2024, Volume:
1058
Journal Article
Peer reviewed
Open access
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The RICH detectors of the LHCb experiment have provided particle identification with excellent performance during Runs 1 and 2 of the LHC . Currently the LHCb experiment is undergoing an upgrade to ...allow, starting from 2021, data collection at 5 times the instantaneous luminosity of the period 2010-2019 (up to 2×1033cm−2s−2 ) with the aim to collect a data sample corresponding to 50 fb−1. The required upgrades to detectors and electronics are significant, with the RICH system changing all of the photon detectors and a full replacement of the upstream RICH detector. The existing Hybrid Photon Detectors (HPD) are being replaced by two types of Multi-Anode Photomultiplier Tubes (MaPMT) with electronics capable of recording data at the full LHC collision frequency of 40 MHz using a time gate of 6 ns. The required 3072 MaPMTs have undergone detailed characterisation, measuring gain and uniformity across channels and the photo-cathode quantum efficiency on a smaller sample. The status of the project will be presented.
A semiconductor tracker for muon scattering tomography is presented. The tracker contains silicon strip sensors with an 80μm pitch, precision mechanics and integrated cooling. The electronic readout ...of the sensors is performed by a scalable, inexpensive, flexible, FPGA-based system, which is demonstrated to achieve an event rate of 30 kHz. The tracker performance is compared with a Geant4 simulation. A scattering angle resolution compatible with 1.5 mrad at the 4 GeV average cosmic ray muon energy is demonstrated. Images of plastic, iron and lead samples are obtained using an Angle Statistics Reconstruction algorithm. The images demonstrate good contrast between low and high atomic number materials.
Abstract
Signal-induced noise is observed in Hamamatsu R11265
Multianode Photomultiplier Tubes, manifesting up to several
microseconds after the single photoelectron response signal and
localised in ...specific anodes. The mean number of noise pulses varies
between devices, and shows significant dependence on the applied
high-voltage. The characterisation of this noise and the mitigation
strategies to perform optimal single-photon counting at 40 MHz, as
required by the LHCb Ring-Imaging Cherenkov detectors, are
reported.
Abstract
The performance of the ring-imaging Cherenkov detectors at
the LHCb experiment is determined during the LHC Run 2 period
between 2015 and 2018. The stability of the Cherenkov angle
...resolution and number of detected photons with time and running
conditions is measured. The particle identification performance is
evaluated with data and found to satisfy the requirements of the
physics programme.
The only anticipated resonant contributions to B^{+}→D^{+}D^{-}K^{+} decays are charmonium states in the D^{+}D^{-} channel. A model-independent analysis, using LHCb proton-proton collision data ...taken at center-of-mass energies of sqrts=7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb^{-1}, is carried out to test this hypothesis. The description of the data assuming that resonances only manifest in decays to the D^{+}D^{-} pair is shown to be incomplete. This constitutes evidence for a new contribution to the decay, potentially one or more new charm-strange resonances in the D^{-}K^{+} channel with masses around 2.9 GeV/c^{2}.
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We present an angular analysis of the B^{+}→K^{*+}(→K_{S}^{0}π^{+})μ^{+}μ^{-} decay using 9 fb^{-1} of pp collision data collected with the LHCb experiment. For the first time, the full set of ...CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B^{0}→K^{*0}μ^{+}μ^{-} decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
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A search for charge-parity (CP) violation in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb^{-1} collected at a ...center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in D^{*}(2010)^{+}→D^{0}π^{+} decays or from the charge of the muon in Bover ¯→D^{0}μ^{-}νover ¯_{μ}X decays. The difference between the CP asymmetries in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays is measured to be ΔA_{CP}=-18.2±3.2(stat)±0.9(syst)×10^{-4} for π-tagged and ΔA_{CP}=-9±8(stat)±5(syst)×10^{-4} for μ-tagged D^{0} mesons. Combining these with previous LHCb results leads to ΔA_{CP}=(-15.4±2.9)×10^{-4}, where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than 5 standard deviations. This is the first observation of CP violation in the decay of charm hadrons.
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Searches are performed for both promptlike and long-lived dark photons, A^{'}, produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for A^{'}→μ^{+}μ^{-} ...decays using a data sample corresponding to an integrated luminosity of 5.5 fb^{-1} collected with the LHCb detector. Neither search finds evidence for a signal, and 90% confidence-level exclusion limits are placed on the γ-A^{'} kinetic mixing strength. The promptlike A^{'} search explores the mass region from near the dimuon threshold up to 70 GeV and places the most stringent constraints to date on dark photons with 214<m(A^{'})≲740 MeV and 10.6<m(A^{'})≲30 GeV. The search for long-lived A^{'}→μ^{+}μ^{-} decays places world-leading constraints on low-mass dark photons with lifetimes O(1) ps.
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