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Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the ...possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop
Tomography of the Quark-Gluon Plasma with Heavy Quarks
, which was held in October 2016 in Leiden, The Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.
First measurements of the performance of the Barrel RPC system in CMS Colaleo, A.; Loddo, F.; Maggi, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2009, Letnik:
609, Številka:
2
Journal Article
Recenzirano
Odprti dostop
During the summer 2006, a first integrated test of a part of the CMS experiment was performed at CERN collecting a data sample of several millions of cosmic rays events. A fraction of the Resistive ...Plate Chambers system was successfully operated. Results on the RPC performance are reported.
The compact muon solenoid RPC barrel detector Colaleo, A.; Loddo, F.; Maggi, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2009, Letnik:
602, Številka:
3
Journal Article
Recenzirano
Resistive Plate Chambers (RPC) have been chosen as dedicated trigger muon detectors for the Compact Muon Solenoid CMS collaboration, Technical Design Report, CERN/LHCC 94-38, 1994.
1 experiment at ...the Large Hadron Collider The LHC project at CERN, LHC-project-report-36, 1996.
2 at CERN.
Four Italian groups from Bari, Frascati, Napoli and Pavia and two Bulgarian groups from Sofia have participated in designing and constructing the RPC barrel system.
A sophisticated and complex production line has been organized by the collaboration to build the 480 RPC chambers, with a quality assurance (QA) test, made by 3 consecutive steps, in order to assure full functionality of the chambers. A final certification of the chambers has been made at ISR (CERN) with a month-long test. After that the RPCs have been coupled to the Drift Tube chamber and installed in the iron return yoke of the CMS solenoid.
The first chamber was produced in 2002 and last was installed in October 2007. The system is now completely installed and commissioning has been going on since the second half of 2005 to complete the Large Hadron Collider (LHC) startup in the summer of 2008.
The chamber construction, the test made, the main results achieved and a short description of all the services needed to run the RPC barrel system will be described in this paper.
The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum (high p_{T}) hadron trigger in proton-proton and ...central Pb-Pb collisions at sqrts_{NN}=5.02 TeV. A data-driven statistical method is used to mitigate the large uncorrelated background in central Pb-Pb collisions. Recoil jet distributions are reported for jet resolution parameter R=0.2, 0.4, and 0.5 in the range 7<p_{T,jet}<140 GeV/c and trigger-recoil jet azimuthal separation π/2<Δφ<π. The measurements exhibit a marked medium-induced jet yield enhancement at low p_{T} and at large azimuthal deviation from Δφ∼π. The enhancement is characterized by its dependence on Δφ, which has a slope that differs from zero by 4.7σ. Comparisons to model calculations incorporating different formulations of jet quenching are reported. These comparisons indicate that the observed yield enhancement arises from the response of the QGP medium to jet propagation.The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum (high p_{T}) hadron trigger in proton-proton and central Pb-Pb collisions at sqrts_{NN}=5.02 TeV. A data-driven statistical method is used to mitigate the large uncorrelated background in central Pb-Pb collisions. Recoil jet distributions are reported for jet resolution parameter R=0.2, 0.4, and 0.5 in the range 7<p_{T,jet}<140 GeV/c and trigger-recoil jet azimuthal separation π/2<Δφ<π. The measurements exhibit a marked medium-induced jet yield enhancement at low p_{T} and at large azimuthal deviation from Δφ∼π. The enhancement is characterized by its dependence on Δφ, which has a slope that differs from zero by 4.7σ. Comparisons to model calculations incorporating different formulations of jet quenching are reported. These comparisons indicate that the observed yield enhancement arises from the response of the QGP medium to jet propagation.
A novel approach for designing the next generation of vertex detectors foresees to employ wafer-scale sensors that can be bent to truly cylindrical geometries after thinning them to thicknesses of ...20–40 μm. To solidify this concept, the feasibility of operating bent MAPS was demonstrated using 1.5cm×3cm ALPIDE chips. Already with their thickness of 50µm, they can be successfully bent to radii of about 2cm without any signs of mechanical or electrical damage. During a subsequent characterisation using a 5.4GeV electron beam, it was further confirmed that they preserve their full electrical functionality as well as particle detection performance.
In this article, the bending procedure and the setup used for characterisation are detailed. Furthermore, the analysis of the beam test, including the measurement of the detection efficiency as a function of beam position and local inclination angle, is discussed. The results show that the sensors maintain their excellent performance after bending to radii of 2cm, with detection efficiencies above 99.9% at typical operating conditions, paving the way towards a new class of detectors with unprecedented low material budget and ideal geometrical properties.
Understanding the role of parton mass and Casimir color factors in the quantum chromodynamics parton shower represents an important step in characterizing the emission properties of heavy quarks. ...Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterize gluon emissions from heavy quarks. In this Letter, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed D^{0} meson. The measurement is made in proton-proton collisions at sqrts=13 TeV, in the low jet transverse-momentum interval of 15≤p_{T}^{jet ch}<30 GeV/c where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, is reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared with gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions.
The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of Formula omitted 7 TeV. The ...measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of Formula omitted in pseudorapidity and a transverse momentum range of Formula omitted. The result extends the Formula omitted coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller Formula omitted. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.
We present a study of the inclusive charged-particle transverse momentum ( Formula omitted) spectra as a function of charged-particle multiplicity density at mid-pseudorapidity, Formula omitted, in ...pp collisions at Formula omitted and 13 TeV covering the kinematic range Formula omitted and Formula omitted GeV/c. The results are presented for events with at least one charged particle in Formula omitted (INEL Formula omitted). The Formula omitted spectra are reported for two multiplicity estimators covering different pseudorapidity regions. The Formula omitted spectra normalized to that for INEL Formula omitted show little energy dependence. Moreover, the high- Formula omitted yields of charged particles increase faster than the charged-particle multiplicity density. The average Formula omitted as a function of multiplicity and transverse spherocity is reported for pp collisions at Formula omitted TeV. For low- (high-) spherocity events, corresponding to jet-like (isotropic) events, the average Formula omitted is higher (smaller) than that measured in INEL Formula omitted pp collisions. Within uncertainties, the functional form of Formula omitted is not affected by the spherocity selection. While EPOS LHC gives a good description of many features of data, PYTHIA overestimates the average Formula omitted in jet-like events.
The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of Formula omitted vector mesons off proton targets in ultra-peripheral p-Pb collisions at a centre-of-mass ...energy per nucleon pair Formula omitted TeV. The e Formula omittede Formula omitted and Formula omitted decay channels are used to measure the cross section as a function of the rapidity of the Formula omitted in the range Formula omitted, corresponding to an energy in the Formula omittedp centre-of-mass in the interval Formula omitted GeV. The measurements, which are consistent with a power law dependence of the exclusive Formula omitted photoproduction cross section, are compared to previous results from HERA and the LHC and to several theoretical models. They are found to be compatible with previous measurements.
The measurements of the production of prompt Formula omitted, Formula omitted, Formula omitted, and Formula omitted mesons in proton-proton (pp) collisions at Formula omitted with the ALICE detector ...at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity ( Formula omitted) via their hadronic decay channels Formula omitted, Formula omitted, Formula omitted, Formula omitted, and their charge conjugates. The production cross sections were measured in the transverse momentum interval Formula omitted for Formula omitted, Formula omitted for Formula omitted and Formula omitted, and in Formula omitted for Formula omitted mesons. Thanks to the higher integrated luminosity, an analysis in finer Formula omitted bins with respect to the previous measurements at Formula omitted was performed, allowing for a more detailed description of the cross-section Formula omitted shape. The measured Formula omitted-differential production cross sections are compared to the results at Formula omitted TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at Formula omitted. This measurement will allow for a more accurate determination of the nuclear modification factor in p-Pb and Pb-Pb collisions performed at the same nucleon-nucleon centre-of-mass energy.
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