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Soft-hard framework with exact four-momentum conservation for small systems
No full textA new framework, called x-scape, for the combined study of both hard and soft transverse momentum sectors in high-energy proton-proton (−) and proton-nucleus (−) collisions is set up. A dynamical initial state is set up using the 3d-Glauber model with transverse locations of hotspots within each incoming nucleon. A hard scattering that emanates from two colliding hotspots is carried out using the Pythia generator. Initial state radiation from the incoming hard partons is carried out in a new module called I-matter, which includes the longitudinal location of initial splits. The energy-momentum of both the initial hard partons and their associated beam remnants is removed from the hot spots, depleting the energy-momentum available for the formation of the bulk medium. Outgoing showers are simulated using the matter generator, and results are presented for both cases, allowing for and not allowing for energy loss. First comparisons between this hard-soft model and single inclusive hadron and jet data from − and minimum bias −Pb collisions are presented. Single hadron spectra in − are used to carry out a limited (in number of parameters) Bayesian calibration of the model. Fair comparisons with data are indicative of the utility of this new framework. Theoretical studies of the correlation between jet and event activity at mid and forward rapidity are carried out
Bayesian inference analysis of jet quenching using inclusive jet and hadron suppression measurements
No full textThe JETSCAPE Collaboration reports a new determination of the jet transport parameter qhat in the quark-gluon plasma (QGP) using Bayesian inference, incorporating all available inclusive hadron and jet yield suppression data measured in heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). This multi-observable analysis extends the previously published JETSCAPE Bayesian inference determination of qhat, which was based solely on a selection of inclusive hadron suppression data. jetscape is a modular framework incorporating detailed dynamical models of QGP formation and evolution, and jet propagation and interaction in the QGP. Virtuality-dependent partonic energy loss in the QGP is modeled as a thermalized weakly coupled plasma, with parameters determined from Bayesian calibration using soft-sector observables. This Bayesian calibration of qhat utilizes active learning, a machine-learning approach, for efficient exploitation of computing resources. The experimental data included in this analysis span a broad range in collision energy and centrality, and in transverse momentum. In order to explore the systematic dependence of the extracted parameter posterior distributions, several different calibrations are reported, based on combined jet and hadron data; on jet or hadron data separately; and on restricted kinematic or centrality ranges of the jet and hadron data. Tension is observed in comparison of these variations, providing new insights into the physics of jet transport in the QGP and its theoretical formulation
Proton emission in ultraperipheral Pb-Pb collisions at TeV
No full textProton emission in ultraperipheral Pb-Pb collisions at sqrt(s_NN) 5.02 TeV
First measurement of = 4 Hypernuclei and Antihypernuclei at the LHC
No full textIn this Letter, the first evidence of the antihypernucleus is presented, along with the first measurement at the LHC of the production of (anti)hypernuclei with mass number , specifically (anti) and (anti). In addition, the antiparticle-to-particle ratios for both hypernuclei ( / and / ) are shown, which are sensitive to the baryochemical potential of the strongly-interacting matter created in heavy-ion collisions. The results are obtained from a data sample of central Pb--Pb collisions, collected during the 2018 LHC data-taking at a center-of-mass energy per nucleon pair of 5.02 TeV. The yields measured for the average of the charge-conjugated states are found to be for the (anti) and for the (anti), and the measured antiparticle-to-particle ratios are in agreement with unity. The presence of (anti) and (anti) excited states is expected to strongly enhance the production yield of these hypernuclei. The yield values exhibit a combined deviation of 3.3 from the theoretical ground-state-only expectation, while the inclusion of the excited states in the calculations leads to an agreement within 0.6 with the present measurements. Additionally, the measured (anti) and (anti) masses are compatible with the world-average values within the uncertainties
Medium-induced modification of groomed and ungroomed jet mass and angularities in Pb–Pb collisions at = 5.02 TeV
No full textThe ALICE Collaboration presents a new suite of jet substructure measurements in Pb–Pb and pp collisions at a center-of-mass energy per nucleon pair = 5.02 TeV. These measurements provide access to the internal structure of jets via the momentum and angle of their constituents, probing how the quark–gluon plasma modifies jets, an effect known as jet quenching. Jet grooming additionally removes soft wide-angle radiation to enhance perturbative accuracy and reduce experimental uncertainties. We report the groomed and ungroomed jet mass and jet angularities using κ = 1 and α > 0. Charged-particle jets are reconstructed at midrapidity using the algorithm with resolution parameter R = 0.2. A narrowing of the jet mass and angularity distributions in Pb–Pb collisions with respect to pp is observed and is enhanced for groomed results, confirming modification of the jet core. By using consistent jet definitions and kinematic cuts between the mass and angularities for the first time, previous inconsistencies in the interpretation of quenching measurements are resolved, rectifying a hurdle for understanding how jet quenching arises from first principles and highlighting the importance of a well-controlled baseline. These results are compared with a variety of theoretical models of jet quenching, providing constraints on jet energy-loss mechanisms in the quark–gluon plasma
Multimuons in cosmic-ray events as seen in ALICE at the LHC
No full textALICE is a large experiment at the CERN Large Hadron Collider. Located 52 meters underground, its detectors are suitable to measure muons produced by cosmic-ray interactions in the atmosphere. In this paper, the studies of the cosmic muons registered by ALICE during Run 2 (2015–2018) are described.The analysis is limited to multimuon events defined as events with more than four detected muons ( > 4) and in the zenith angle range 0° 100) obtainedwith QGSJET-II-04 and SIBYLL 2.3d is compatible with the data, while EPOS-LHC produces a significantly lower rate (55% of the measured rate). For both QGSJET-II-04 and SIBYLL 2.3d, the rate is close to the data when the composition is assumed to be dominated by heavy elements, an outcome compatible with the average energy E ∼ 10 eV of these events.This result places significant constraints on more exotic production mechanisms
Modular Experiment Control System packages for the CBM experiment
No full textThe Compressed Baryonic Matter (CBM) is a fixed-target experiment which will explore the QCD phase diagram through heavy-ions collisions using the beams from the SIS100 accelerator at FAIR. Its physics program characteristics led to a choice for a self-triggered and free-streaming data acquisition, followed by an online full reconstruction and selection chain in software. Such a system can operate reliably and efficiently only with a performant Experiment Control System (ECS) to ensure the synchronization and data quality of all sub-systems. The development of a CBM-specific Python based solution, focused only on the Experiment Controls and on the upper layer of Detector Controls (state and configuration propagation), was chosen after looking at existing solutions. It is divided in three packages, from an experiment independent modular core to user interfaces, in order to allow maximal quality checks of the core functions. This article presents the design choices for this ECS, the technical core package, the CBM ECS implementation package and the demonstrator GUI package based on it. All three packages are now available in demonstrator versions, with test coverage and typing coverage both above 90% for the core package. They will be deployed for validation in the CBM demonstrator, mini-CBM (mCBM)
Current status of the MYRRHA project at IAP Frankfurt
No full textAs part of the MYRRHA project, which is being implemented in Mol, Belgium, two of the planned 17 normal-conducting CH cavities have been built and tested at several kilowatts of RF power. Since the cooling concept for the stems was revised after their construction, concerns arose that the two existing cavities might have suffered a degradation in performance during high-power testing due to the outdated cooling system. Consequently, it was decided to subject cavity CH02 to renewed LLRF measurements at IAP Frankfurt to ensure that its performance has not deteriorated. The cavity is then scheduled for high-power testing at the newly established high-power station at IAP. This will not only serve to commission the test stand but also recondition the cavity This paper summarizes the recent LLRF measurements performed on CH02 and reports on the current status of preparations for the upcoming conditioning
Current status of beam commissioning at the Frankfurt Neutron Source
No full textThe Frankfurt Neutron Source FRANZ will be a compact accelerator driven neutron source utilizing the 7Li(p,n)7Be reaction with a 2 MeV proton beam. The 700 keV RFQ has been sucessfully commissioned with a 10 mA proton beam. Conditioning of the subsequent IH-type cavity has been performed up to 10 kW. We also report on RFQ emittance measurements performed with a slit grid emittance device. In addition, a fast faraday cup (FFC) was used for bunch shape measurements behind the RFQ