Progress towards the first measurement of charm baryon dipole moments

Electromagnetic dipole moments of short-lived particles are sensitive to physics within and beyond the Standard Model of particle physics but have not been accessible experimentally to date. To perform such measurements it has been proposed to exploit the spin precession of channeled particles in bent crystals at the LHC. Progress that enables the first measurement of charm baryon dipole moments is reported. In particular, the design and characterization on beam of silicon and germanium bent crystal prototypes, the optimization of the experimental setup, and advanced analysis techniques are discussed. Sensitivity studies show that first measurements of Λ+c and Ξ+c baryon dipole moments can be performed in two years of data taking with an experimental setup positioned upstream of the LHCb detector. Figur

Performance of a spaghetti calorimeter prototype with tungsten absorber and garnet crystal fibres

A spaghetti calorimeter (SPACAL) prototype with scintillating crystal fibres was assembled and tested with electron beams of energy from 1 to 5 GeV. The prototype comprised radiation-hard Cerium-doped GdAlGaO (GAGG:Ce) and YAlO (YAG:Ce) embedded in a pure tungsten absorber. The energy resolution was studied as a function of the incidence angle of the beam and found to be of the order of 10%/E⊕1%, in line with the LHCb Shashlik technology. The time resolution was measured with metal channel dynode photomultipliers placed in contact with the fibres or coupled via a light guide, additionally testing an optical tape to glue the components. Time resolution of a few tens of picosecond was achieved for all the energies reaching down to (18.5 ± 0.2) ps at 5 GeV.We acknowledge support by the CERN Strategic Programme on Technologies for Future Experiments, https://ep-rnd.web.cern.ch/, by the MCIN/AEI, GenCat and GVA (Spain), and by the NSFC (China) under grant Nos. 12175005, 12061141007. The measurements were performed at the Test Beam Facility at DESY Hamburg (Germany), a member of the Helmholtz Association (HGF). The authors would like to thank T. Schneider, H. Gerwig, N. Siegrist, and D. Deyrail (CERN) for their help in designing and assembling the prototype and the set-up, A. Barnyakov, Budker Institute of Nuclear Physics (BINP), Novosibirsk, for kindly providing the MCPs, and the ITEP ATLAS group for the DWCs

RD50-MPW: a series of monolithic High Voltage CMOS pixel chips with high granularity and towards high radiation tolerance

Abstract A series of monolithic High Voltage CMOS (HV-CMOS) pixel sensor prototypes have been developed by the CERN-RD50 CMOS working group for potential use in future high luminosity experiments. The aim is to further improve the performance of HV-CMOS sensors, especially in terms of pixel granularity, timing resolution and radiation tolerance. The evaluation of one of this series, RD50-MPW3, is presented in this contribution, including laboratory and test beam measurements. The design of the latest prototype, RD50-MPW4, which resolves issues found in RD50-MPW3 and implements further improvements, is described. </jats:p

Study of b-hadron decays to Λc^+h-h' final states

Decays of Ξ − b and Ω − b baryons to Λ + c h −h ′− final states, with h −h ′− being π −π −, K−π\ud − and K−K− meson pairs, are searched for using data collected with the LHCb detector. The data sample studied corresponds to an integrated luminosity of 8.7 fb−1 of pp collisions collected at centre-of-mass energies √ s = 7, 8 and 13 TeV. The products of the relative branching fractions and fragmentation fractions for each signal mode, relative to the B− → Λ + c pπ− mode, are measured, with Ξ − b → Λ + c K−π −, Ξ − b → Λ + c K−K− and Ω − b → Λ + c K−K− decays being observed at over 5 σ significance. The Ξ − b → Λ + c K−π − mode is also used to measure the Ξ − b production asymmetry, which is found to be consistent with zero. In addition, the B− → Λ + c pK− decay is observed for the first time, and its branching fraction is measured relative to that of the B− → Λ + c pπ− mode

The LHCb upgrade I

The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

RD50-MPW3: a fully monolithic digital CMOS sensor for future tracking detectors

Abstract The CERN-RD50 CMOS working group develops the RD50-MPW series of monolithic high-voltage CMOS pixel sensors for potential use in future high luminosity experiments such as the HL-LHC and FCC-hh. In this contribution, the design of the latest prototype in this series, RD50-MPW3, is presented. An overview of its pixel matrix and digital readout periphery is given, with discussion of the new structures implemented in the chip and the problems they aim to solve. The main analogue and digital features of the sensor are already tested and initial laboratory characterisation of the chip is presented.</jats:p

Progress towards the first measurement of charm baryon dipole moments

21sinoneElectromagnetic dipole moments of short-lived particles are sensitive to physics within and beyond the Standard Model of particle physics but have not been accessible experimentally to date. To perform such measurements it has been proposed to exploit the spin precession of channeled particles in bent crystals at the LHC. Progress that enables the first measurement of charm baryon dipole moments is reported. In particular, the design and characterization on beam of silicon and germanium bent crystal prototypes, the optimization of the experimental setup, and advanced analysis techniques are discussed. Sensitivity studies show that first measurements of Λc+ and Ξc+ baryon dipole moments can be performed in two years of data taking with an experimental setup positioned upstream of the LHCb detector.noneAiola S.; Bandiera L.; Cavoto G.; De Benedetti F.; Fu J.; Guidi V.; Henry L.; Marangotto D.; Martinez Vidal F.; Mascagna V.; Mazorra De Cos J.; Mazzolari A.; Merli A.; Neri N.; Prest M.; Romagnoni M.; Ruiz Vidal J.; Soldani M.; Sytov A.; Tikhomirov V.; Vallazza E.Aiola, S.; Bandiera, L.; Cavoto, G.; De Benedetti, F.; Fu, J.; Guidi, V.; Henry, L.; Marangotto, D.; Martinez Vidal, F.; Mascagna, V.; Mazorra De Cos, J.; Mazzolari, A.; Merli, A.; Neri, N.; Prest, M.; Romagnoni, M.; Ruiz Vidal, J.; Soldani, M.; Sytov, A.; Tikhomirov, V.; Vallazza, E

The DMAPS upgrade of the Belle II vertex detector

International audienceThe SuperKEKB collider will undergo a major upgrade to reach the target luminosity of 6 × 10$^{35}$ cm$^{-2}$ s$^{-1}$ during the long shutdown (LS2) foreseen to start around year 2027. We are developing a new vertex detector (VTX) to replace the current one (VXD). This new pixel silicon tracker aims to be both more robust against the higher level of machine background and more performant in terms of precision on the decay vertices and standalone track finding efficiency. The baseline layout consists of two layers composing the inner part (iVTX) and three outer layers (oVTX), all arranged in a barrel-shaped geometry, with minimal material budget. All layers will be equipped with dedicated depleted monolithic active CMOS pixel sensors (DMAPS) named OBELIX, designed in the TowerJazz 180 nm technology. This paper will review all the aspects of the project: the detector specifications and the baseline design, the expected improved performance, the OBELIX features and its design status, including the tests of the forerunner chip TJ-Monopix2, and the fabrication and tests for the iVTX and oVTX ladder prototypes

The DMAPS upgrade of the Belle II vertex detector

International audienceThe Belle II experiment at KEK in Japan considers an upgrade for the vertex detector system in line with the accelerator upgrade for higher luminosity at long shutdown 2 planned for 2028. One proposal for the upgrade of the vertex detector called VTX aims to improve background robustness and reduce occupancy using small and fast pixels. VTX accommodates the OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) on all five proposed layers. OBELIX is specifically developed for the VTX application and based on the TJ-Monopix2 chip initially developed to meet the requirements of the outer layers of the ATLAS inner tracker (ITk). This paper will review recent tests of the TJ-Monopix2 chip as well as various design aspects of the OBELIX-1 chip currently under development

Design of the OBELIX monolithic CMOS pixel sensor for an upgrade of the Belle II vertex detector

International audienceThe Belle II collaboration has initiated a program to upgrade its detector in order to address the challenges set by the increase of the SuperKEKB collider luminosity, targeting 6×10$^{35}$ cm$^{2}$ s$^{-1}$. A monolithic CMOS pixel sensor named OBELIX (Optimized BELle II pIXel) is proposed to equip 5 detection layers upgrading the current vertex detector. Based on the existing TJ-Monopix2, OBELIX is currently designed in 180 nm CMOS process