Phase Equilibrium and Synthesis in Ionic Melts of the System Na2WO4-K2WO4-Pb2WO4

Interest in a comprehensive study of lead tungstate single crystals is due to its scintillation properties [1-5]. It was found that lead tungstate occupies an exceptional position in the family of tungstates with a scheelite structure. Lead tungstate single crystal is a scintillation material [1] used in the LHC electromagnetic calorimeter and photon detector in the ALICE experiment at CERN [1, 2]. Now it can be said unequivocally that lead tungstate is the most promising scintillation material in the next decade.

Development, construction and tests of the Mu2e electromagnetic calorimeter mechanical structures

The “muon-to-electron conversion” (Mu2e) experiment at Fermilab will search for the charged lepton flavour violating neutrino-less coherent conversion of a muon into an electron in the field of an aluminum nucleus. The observation of this process would be the unambiguous evidence of the existence of physics beyond the standard model. Mu2e detectors comprise a straw-tracker, an electromagnetic calorimeter and an external veto for cosmic rays. In particular, the calorimeter provides excellent electron identification, a fast calorimetric online trigger, and complementary information to aid pattern recognition and track reconstruction. The detector has been designed as a state-of-the-art crystal calorimeter and employs 1348 pure Cesium Iodide (CsI) crystals readout by UV-extended silicon photosensors and fast front-end and digitization electronics. A design consisting of two identical annular matrices (named “disks”) positioned at the relative distance of 70 cm downstream the aluminum target along the muon beamline satisfies the Mu2e physics requirements. The hostile Mu2e operational conditions, in terms of radiation levels (total expected ionizing dose of 12 krad and a neutron fluence of 5 × 1010 n/cm2 @ 1 MeVeq (Si)/y), magnetic field intensity (1 T) and vacuum level (10−4 Torr) have posed tight constraints on scintillating materials, sensors, electronics and on the design of the detector mechanical structures and material choice. The support structure of each 674 crystal matrix is composed of an aluminum hollow ring and parts made of open-cell vacuum-compatible carbon fiber. The photosensors and front-end electronics for the readout of each crystal are inserted in a machined copper holder and make a unique mechanical unit. The resulting 674 mechanical units are supported by a machined plate of vacuum-compatible plastic material. The plate also integrates the cooling system made of a network of copper lines flowing a low temperature radiation-hard fluid and placed in thermal contact with the copper holders to constitute a low resistance thermal bridge. The data acquisition electronics are hosted in aluminum custom crates positioned on the external lateral surface of the disks. The crates also integrate the electronics cooling system as lines running in parallel to the front-end system. In this paper we report on the calorimeter mechanical structure design, the mechanical and thermal simulations that have determined the design technological choices, and the status of component production, quality assurance tests and plans for assembly at Fermilab.

The CMS electromagnetic calorimeter upgrade: high-rate readout with precise time and energy resolution

The electromagnetic calorimeter (ECAL) of the CMS detector has played an important role in the physics program of the experiment, delivering outstanding performance throughout data taking. The high-luminosity LHC will pose new challenges. The four to five-fold increase of the number of interactions per bunch crossing will require superior time resolution and noise rejection capabilities. For these reasons the electronics readout has been completely redesigned. A dual gain trans-impedance amplifier and an ASIC providing two 160 MHz ADC channels, gain selection, and data compression will be used in the new readout electronics. The trigger decision will be moved off-detector and will be performed by powerful and flexible FPGA processors, allowing for more sophisticated trigger algorithms to be applied. The upgraded ECAL will be capable of high-precision energy measurements throughout HL-LHC and will greatly improve the time resolution for photons and electrons above 10 GeV.

Use of Deep Learning to Improve the Computational Complexity of Reconstruction Algorithms in High Energy Physics

The optimization of reconstruction algorithms has become a key aspect in the field of experimental particle physics. Since technology has allowed gradually increasing the complexity of the measurements, the amount of data taken that needs to be interpreted has grown as well. This is the case with the LHCb experiment at CERN, where a major upgrade currently undergoing will considerably increase the data processing rate. This has presented the need to search for specific reconstruction techniques that aim to accelerate one of the most time consuming reconstruction algorithms in LHCb, the electromagnetic calorimeter clustering. Together with the use of deep learning techniques and the understanding of the current reconstruction algorithm, we propose a method that decomposes the reconstruction process into small parts that can be formulated as a cellular automaton. This approach is shown to benefit the generalized learning of small convolutional neural network architectures and also simplify the training dataset. Final results applied to a complete LHCb simulation reconstruction are compatible in terms of efficiency, and execute in nearly constant time with independence on the complexity of the data.

SiPM dynamic range for CEPC scintillator-based electromagnetic calorimeter

A high-granularity scintillator calorimeter readout with silicon photomultipliers (SiPMs) is an electromagnetic calorimeter (ECAL) candidate for experiments at the Circular Electron Positron Collider (CEPC). A critical design parameter of this ECAL candidate is the dynamic range of the SiPMs. This study investigates the SiPM dynamic range required for the CEPC scintillator ECAL. A model is developed on the basis of the operation principles of SiPMs to describe the response of an SiPM to light pulses within one recovery period by considering the cross-talk effect, photon detection efficiency, and number of pixels. The response curve of a 10000-pixel SiPM predicted by the model is consistent with the measured curve within 2% for an incident light pulse of up to 12000 photons. The intrinsic fluctuations of the SiPM response naturally exist in this model, and the correction of the saturation effect in the SiPM response is investigated. Monte Carlo (MC) simulation shows that the algorithm can restore the response linearity of an SiPM for an incident light pulse in which the number of photons is up to around six times the number of SiPM pixels. The model and correction program are implemented for full simulation of the ZH production Z → νν, H → γγ channel to evaluate the impact of the SiPM dynamic range of the CEPC scintillator ECAL on the reconstructed Higgs boson mass and the sensitivity to the Higgs signal in this channel. The results show that the CEPC scintillator ECAL equipped with no less than 4000 SiPM pixels and operated with a light yield of 20 photon-electrons per channel for a single minimum ionizing particle can meet the requirements for Higgs boson precision measurement in the di-photon channel at the CEPC.

Inclusive $$\text {J}/\psi $$ production at midrapidity in pp collisions at $$\sqrt{s} = 13$$ TeV

We report on the inclusive $$\text {J}/\psi $$ J / ψ production cross section measured at the CERN Large Hadron Collider in proton–proton collisions at a center-of-mass energy $$\sqrt{s}~=~13$$ s = 13 TeV. The $$\text {J}/\psi $$ J / ψ mesons are reconstructed in the $$\text {e}^{+}\text {e}^{-}$$ e + e - decay channel and the measurements are performed at midrapidity ($$|y|<0.9$$ | y | < 0.9 ) in the transverse-momentum interval $$0<p_{\mathrm{T}} <40$$ 0 < p T < 40 GeV/$$c$$ c , using a minimum-bias data sample corresponding to an integrated luminosity $$L_{\text {int}} = 32.2~\text {nb}^{-1}$$ L int = 32.2 nb - 1 and an Electromagnetic Calorimeter triggered data sample with $$L_{\text {int}} = 8.3~\mathrm {pb}^{-1}$$ L int = 8.3 pb - 1 . The $$p_{\mathrm{T}}$$ p T -integrated $$\text {J}/\psi $$ J / ψ production cross section at midrapidity, computed using the minimum-bias data sample, is $$\text {d}\sigma /\text {d}y|_{y=0} = 8.97\pm 0.24~(\text {stat})\pm 0.48~(\text {syst})\pm 0.15~(\text {lumi})~\mu \text {b}$$ d σ / d y | y = 0 = 8.97 ± 0.24 ( stat ) ± 0.48 ( syst ) ± 0.15 ( lumi ) μ b . An approximate logarithmic dependence with the collision energy is suggested by these results and available world data, in agreement with model predictions. The integrated and $$p_{\mathrm{T}}$$ p T -differential measurements are compared with measurements in pp collisions at lower energies and with several recent phenomenological calculations based on the non-relativistic QCD and Color Evaporation models.

Studies of high-field QED with the LUXE experiment at the European XFEL

The LUXE experiment aims at studying high-field QED in electron-laser and photon-laser interactions, with the 16.5 GeV electron beam of the European XFEL and a laser beam with power of up to 350 TW. The experiment will measure the spectra of electrons and photons in non-linear Compton scattering where production rates in excess of 109 are expected per 1 Hz bunch crossing. At the same time positrons from pair creation in either the two-step trident process or the Breit-Wheeler process will be measured, where the expected rates range from 10−3 to 104 per bunch crossing, depending on the laser power and focus. These measurements have to be performed in the presence of low-energy high radiation-background. To meet these challenges, for high-rate electron and photon fluxes, the experiment will use Cherenkov radiation detectors, scintillator screens, sapphire sensors as well as lead-glass monitors for back-scattering off the beam-dump. A four-layer silicon-pixel tracker and a compact sampling electromagnetic calorimeter will be used to measure the positron spectra. The layout of the experiment and the expected performance under the harsh radiation conditions will be presented.

Determination of Position Resolution for LYSO Scintillation Crystals Using Geant4 Monte Carlo Code

LYSO scintillation crystals, due to their significant characteristics such as high light yield, fast decay time, small Moliére radius, and good radiation hardness, are proposed to be used for the electromagnetic calorimeter section of the Turkish Accelerator Center Particle Factory (TAC-PF) detector. In this work, the center of gravity technique was used to determine the impact coordinates of an electron initiating an electromagnetic shower in a LYSO array, in a calorimeter module containing nine crystals, each 25 mm × 25 mm in cross-section and 200 mm in length. The response of the calorimeter module has been studied with electrons having energies in the range 0.1 GeV-2 GeV. By using the Monte Carlo simulation based on Geant4, the two-dimensional position resolution of the module is obtained as σ R mm = 3.95 ± 0.08 / E ⊕ 1.91 ± 0.11 at the center of the crystal.

Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at $$ \sqrt{s} $$, $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

Jet fragmentation transverse momentum (jT) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm with resolution parameter R = 0.4 in the pseudorapidity range |η| < 0.25. The jT values are calculated for charged particles inside a fixed cone with a radius R = 0.4 around the reconstructed jet axis. The measured jT distributions are compared with a variety of parton-shower models. Herwig and Pythia 8 based models describe the data well for the higher jT region, while they underestimate the lower jT region. The jT distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher jT values (called the “wide component”), related to the perturbative component of the fragmentation process, and with a Gaussian for lower jT values (called the “narrow component”), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.