Neutron irradiation test on ATLAS MDT chambers

Abstract The Monitored Drift Tubes (MDT) chambers of the ATLAS muon spectrometer are crucial for the identification of high-momentum final-state muons, which represent very promising and robust signatures of physics at the LHC. They will operate in a high rate and high background environment and therefore their performances should not significantly degrade for the whole ATLAS data taking. The maximum expected total flux, mainly consisting of neutrons and photons in the MeV range, is of the order of 5 kHz/cm 2 for the barrel MDTs, while at SLHC, with machine working at higher luminosity, fluxes can be 10 times higher. To test detector robustness, a MDT test chamber was exposed to intensive neutron irradiation at the TAPIRO ENEA-Casaccia Research Center facility

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb${ }^{-1}$ of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

The micro-Resis7ve WELL detector for the phase 2 upgrade of the LHCb muon detector

he LHCb experiment is a single-arm spectrometer dedicated to the study of the CP viola7on and other rare phenomena in the decay of Beauty par7cles. One of its feature is a fast and versa7le trigger system to select the interes7ng events. The apparatus is designed like a fixed-target experiment due to the very forward peaked b-quark distribu7on at LHC. It is composed of five systems: vertexing, tracking, ring cherenkov detectors, the calorimeters and the muon system. Up to the end of 2017 LHCb has recorded a total luminosity of 7 g-1 and in the next year, since LHC is going to increase its luminosity, the apparatus needs to upgrade its system. For the first phase only the replacement of the FEE will be done. For the phase 2, the detectors should show a rate capability up to 3 MHz/cm2, an efficiency for single gap > 95% within 25 ns (BX), stability up to 6 C/cm2 integrated charge in 10 y at G=4000. So we propose for this upgrade the micro-Resis7ve WELL

Search for a light U boson in e+e− → μ+μ−γ channel with the KLOE experiment at DAΦNE collider at LNF and application of the GEM technology for the KLOE-2 Inner Tracker

Dottorato di Ricerca in Fisica, Ciclo XXIII, a.a 2009-2010L’esperimento KLOE ai Laboratori Nazionali di Frascati ha accumulato una luminosit`a integrata di R L dt 2.5 fb−1 (nel periodo 2002-2005) alla - factory DA NE, un acceleratore e+e− con energia nel centro di massa di 1020 MeV corrispondente alla massa del mesone . L’esperimento ha for- nito molteplici misure di precisione nella fisica dei kaoni e degli adroni. Un upgrade del rivelatore KLOE con nuovi rivelatori `e stato approvato e KLOE- 2 inizier`a la presa dati in pochi mesi (inizio del 2011). Il programma di fisica di KLOE-2 si focalizzer`a sull’interferometria dei kaoni neutri, sugli studi dei decadimenti del KS, e ′ e su un nuovo bosone di gauge previsto in alcune estensioni del Modello Standard. Nel primo capitolo troviamo una sintesi della fisica dell’interferometria dei kaoni neutri e sono introdotte le ragioni per ricerche di Dark Matter a KLOE e KLOE-2. Questa ricerca ha una semplice segnatura (una coppia di muoni con fotone associato) che sar`a descritta in dettaglio nell’ultima parte del capi- tolo. La descrizione dell’apparato sperimentale KLOE sar`a data nel secondo capi- tolo: le caratteristiche della Camera a Deriva, del Calorimetro e del sistema di Trigger saranno riportate. Il programma KLOE-2 sar`a introdotto nel terzo capitolo, con una descrizione dei nuovi rivelatori previsti nell’apparato. In particolare, l’inserimento di un Tracciatore Interno sar`a presentato, oltre all’impatto sulle misure di fisica. Nel quarto capitolo si discuter`a della tecnologia (GEM) che `e stata usata per realizzare il Tracciatore Interno. I principali vantaggi di questa tecnologia saranno spiegati, per finire con un breve sguardo sulle nuove tecniche in fase di sviluppo. Il quinto capitolo si occuper`a della contruzione del prototipo del Tracciatore Interno con la tecnologia GEM e delle misure fatte su di esso. La parte finale del capitolo sar`a centrata sulla caratterizzazione del comportamento di una GEM planare in campo magnetico con il readout finale progettato per il TI. Nell’ultimo capitolo si discuter`a in dettaglio l’analisi per la ricerca di un bosone leggero (U) negli eventi μμ a sar`a presentato un nuovo taglio che `e 1 stato sviluppato per migliorare la reiezione del fondo (principalmente eventiUniversità della Calabri

The micro-RWELL detector for the LHCb Muon system phase-2 upgrade

The micro-RWELL is a single amplification stage resistive Micro-Pattern Gaseous Detector, realized with a copper-clad polyimide foil patterned with a micro-well matrix and coupled with the readout PCB through a DLC resistive film ($10\div100$ MOhm/$\square$). The detector is proposed for several applications in HEP that require fast and efficient triggering in harsh environment (LHCb muon-upgrade), low mass fine tracking (FCC-ee, CepC) or high granularity imaging for hadron calorimeter applications (Muon collider). For the phase-2 upgrade of the LHCb experiment, proposed for LHC Run-5, the excellent performance of the current muon detector will need to be maintained at 40 times the pile-up level experienced during Run-2. Requirements are challenging for the innermost regions of the muon stations, where detectors with rate capability up to 1 MHz/cm$^2$ and capable to stand an integrated charge up to 10 C/cm$^2$ are needed. In this framework an intense optimization program of the micro-RWELL has been launched in the last years, together with a technology transfer to the industry operating in the PCB field. In order to fulfill the requirements, a new layout of the detector with a very dense current evacuation grid of the DLC has been designed. The detector, co-produced by the CERN-EP-DT-MPT Workshop and the ELTOS Company, has been characterized in terms of rate capability exploiting a high intensity 5.9 keV X-ray gun with a spot size ($10\div50$ mm diameter) larger than the DLC grounding-pitch. A rate capability exceeding 10 MHz/cm$^2$ has been achieved, in agreement with previous results obtained with m.i.p. at PSI

A Highschooler’s Guide to GeV-Range Electromagnetism

The following article has been written primarily by the high school students who make up the team “Cryptic Ontics”, one of the two winning teams in the 2018 edition of CERN’s Beamline for Schools (BL4S) competition, and is based on the set of experiments the students endeavoured to conduct over the course of a two-week period at CERN. Reconstructing influential physical theories from scratch often helps in uncovering hitherto unknown logical connections and eliciting instructive empirical checkpoints within said theory. With this in mind, in the following article, a top-down reconstruction (beginning with the experimental observations and ending at the theoretical framework) of the Lorentz force equation is performed, and potentially interesting questions which come up are explored. In its most common form, the equation is written out as: [Formula: see text]. Only the term that includes the magnetic field [Formula: see text] will be dealt with for this article. The independent parameters we use are (i) the momenta of the particles, (ii) the charge (rather, the types) of particles, either positive or negative, and (iii) the current passing through the dipole generating the electromagnetic field. We then measure the angle by which particles get deflected while varying these three parameters and derive an empirical relationship between them

Advances on micro-RWELL gaseous detector

The R&D; on the micro-Resistive-WELL ($\mu$-RWELL) detector technology aims in developing a new scalable, compact, spark-protected, single amplification stage Micro-Pattern Gas Detectors (MPGD) for large area HEP applications as tracking and calorimeter device as well as for industrial and medical applications as X-ray and neutron imaging gas pixel detector. The novel micro- structure, exploiting several solutions and improvements achieved in the last years for MPGDs, in particular for GEMs and Micromegas, is an extremely simple detector allowing an easy engineering with consequent technological transfer toward the photolithography industry. Large area detectors (up $1 \times 2 m^2$) can be realized splicing $\mu$-RWELL_PCB tiles of smaller size (about $0.5 \times 1 m^2$ - typical PCB industrial size). The detector, composed by few basic elements such as the readout-PCB embedded with the amplification stage (through the resistive layer) and the cathode defining the gas drift-conversion gap has been largely characterized on test bench with X-ray and with beam test