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Bellini, F.

Publications and source records attributed to Bellini, F..

At least 271 records · Page 15
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DOE OSTI2018

Λ c + production in pp collisions at $ \sqrt{s}=7 $ TeV and in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV

The p T -differential production cross section of prompt Λ c + charmed baryons was measured with the ALICE detector at the Large Hadron Collider (LHC) in pp collisions at √s = 7 TeV and in p-Pb collisions at √ S NN = 5.02 TeV at midrapidity. The Λ c + and Λ¯ c¯ were reconstructed in the hadronic decay modes Λ c + → pK – π+, Λ c + → pK S 0 and in the semileptonic channel Λ c + → e+ν e Λ (and charge conjugates). The measured values of the Λ c + /D 0 ratio, which is sensitive to the c-quark hadronisation mechanism, and in particular to the production of baryons, are presented and are larger than those measured previously in different colliding systems, centre-of-mass energies, rapidity and p T intervals, where the Λ c + production process may differ. The results are compared with the expectations obtained from perturbative Quantum Chromodynamics calculations and Monte Carlo event generators. Neither perturbative QCD calculations nor Monte Carlo models reproduce the data, indicating that the fragmentation of heavy-flavour baryons is not well understood. The first measurement at the LHC of the Λ c + nuclear modification factor, R pPb , is also presented. Furthermore, the R pPb is found to be consistent with unity and with that of D mesons within the uncertainties, and consistent with a theoretical calculation that includes cold nuclear matter effects and a calculation that includes charm quark interactions with a deconfined medium.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

First Results from CUORE: A Search for Lepton Number Violation via 0 ν β β Decay of Te 130

The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this technology, and in this work we apply it for the first time to a high-sensitivity search for a lepton-numberviolating process: 130 Te neutrinoless double-beta decay. Examining a total TeO 2 exposure of 86.3 kg yr, characterized by an effective energy resolution of d7.7 ± 0.5T keV FWHM and a background in the region of interest of d0.014 ± 0.002T counts=dkeV kg yrT, we find no evidence for neutrinoless double-beta decay. Including systematic uncertainties, we place a lower limit on the decay half-life of T 0ν 1/2 ( 130 Te) > 1.3 × 10 25 yr (90% C.L.); the median statistical sensitivity of this search is 7.0 × 10 24 yr. Combining this result with those of two earlier experiments, Cuoricino and CUORE-0, we find T 0ν 1/2 ( 130 Te) > 1.5 × 10 25 yr (90% C.L.), which is the most stringent limit to date on this decay. Interpreting this result as a limit on the effective Majorana neutrino mass, we find m ββ < (110 - 520) meV, where the range reflects the nuclear matrix element estimates employed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

π 0 and η meson production in proton-proton collisions at $\sqrt{s}=8$ TeV

For this, an invariant differential cross section measurement of inclusive π 0 and η meson production at mid-rapidity in pp collisions at $\sqrt{s}=8$ TeV was carried out by the ALICE experiment at the LHC. The spectra of π 0 and η mesons were measured in transverse momentum ranges of 0.3 < p T < 35 GeV/c and 0.5 < p T <35 GeV/c, respectively. Next-to-leading order perturbative QCD calculations using fragmentation functions DSS14 for the π 0 and AESSS for the η overestimate the cross sections of both neutral mesons, although such calculations agree with the measured η/π 0 ratio within uncertainties. The results were also compared with PYTHIA 8.2 predictions for which the Monash 2013 tune yields the best agreement with the measured neutral meson spectra. The measurements confirm a universal behavior of the η/π 0 ratio seen for NA27, PHENIX and ALICE data for pp collisions from $\sqrt{s}=27.5$ GeV to $\sqrt{s}=8$ TeV within experimental uncertainties. A relation between the π 0 and η production cross sections for pp collisions at $\sqrt{s}=8$ TeV is given by m T scaling for p T > 3.5 GeV/c . However, a deviation from this empirical scaling rule is observed for transverse momenta below p T < 3.5 GeV/c in the η/π 0 ratio with a significance of 6.2σ .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Kaon femtoscopy in Pb-Pb collisions at s NN = 2.76 TeV

Here, we present the results of three-dimensional femtoscopic analyses for charged and neutral kaons recorded by ALICE in Pb-Pb collisions at s NN =2.76 TeV. Femtoscopy is used to measure the space-time characteristics of particle production from the effects of quantum statistics and final-state interactions in two-particle correlations. Kaon femtoscopy is an important supplement to that of pions because it allows one to distinguish between different model scenarios working equally well for pions. In particular, we compare the measured three-dimensional kaon radii with a purely hydrodynamical calculation and a model where the hydrodynamic phase is followed by a hadronic rescattering stage. The former predicts an approximate transverse mass (m T ) scaling of source radii obtained from pion and kaon correlations. This m T scaling appears to be broken in our data, which indicates the importance of the hadronic rescattering phase at LHC energies. A k T scaling of pion and kaon source radii is observed instead. The time of maximal emission of the system is estimated by using the three-dimensional femtoscopic analysis for kaons. The measured emission time is larger than that of pions. Our observation is well supported by the hydrokinetic model predictions.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Charged-particle multiplicity distributions over a wide pseudorapidity range in proton-proton collisions at $\sqrt{s}=$ = 0.9, 7, and 8 TeV

Here, we present the charged-particle multiplicity distributions over a wide pseudorapidity range (-3.4 <η< 5.0) for pp collisions at $\sqrt{s}=$=0.9,7, and 8 TeV at the LHC. Results are based on information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE, extending the pseudorapidity coverage of the earlier publications and the high-multiplicity reach. The measurements are compared to results from the CMS experiment and to PYTHIA, PHOJET and EPOS LHC event generators, as well as IP-Glasma calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

First measurement of jet mass in Pb–Pb and p–Pb collisions at the LHC

This letter presents the first measurement of jet mass in Pb–Pb and p–Pb collisions at $\sqrt{s}$$_ {NN}$ =2.76 TeV and $\sqrt{s}$$_ {NN}$ =5.02 TeV, respectively. Both the jet energy and the jet mass are expected to be sensitive to jet quenching in the hot Quantum Chromodynamics (QCD) matter created in nuclear collisions at collider energies. Jets are reconstructed from charged particles using the anti-k T jet algorithm and resolution parameter R=0.4. The jets are measured in the pseudorapidity range |η jet | < 0.5 and in three intervals of transverse momentum between 60 GeV/c and 120 GeV/c. The measurement of the jet mass in central Pb–Pb collisions is compared to the jet mass as measured in p–Pb reference collisions, to vacuum event generators, and to models including jet quenching. It is observed that the jet mass in central Pb–Pb collisions is consistent within uncertainties with p–Pb reference measurements. Furthermore, the measured jet mass in Pb–Pb collisions is not reproduced by the quenching models considered here and is found to be consistent with PYTHIA expectations within systematic uncertainties.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Measurement of deuteron spectra and elliptic flow in Pb–Pb collisions at $\sqrt{s_{\mathrm {NN}}}$ = 2.76 TeV at the LHC

The transverse momentum (p T ) spectra and elliptic flow coefficient (v 2 ) of deuterons and anti-deuterons at mid-rapidity (|y|<0.5) are measured with the ALICE detector at the LHC in Pb–Pb collisions at $\sqrt{s}$ NN = 2.76 TeV. The measurement of the p T spectra of (anti-)deuterons is done up to 8 GeV/c in 0–10% centrality class and up to 6 GeV/c in 10–20% and 20–40% centrality classes. The v 2 is measured in the 0.8 < p T < 5 GeV/c interval and in six different centrality intervals (0–5, 5–10, 10–20, 20–30, 30–40 and 40–50%) using the scalar product technique. Measured π ± , K ± and p+$\bar{p}$ transverse-momentum spectra and v 2 are used to predict the deuteron p T spectra and v 2 within the Blast-Wave model. The predictions are able to reproduce the v 2 coefficient in the measured p T range and the transverse-momentum spectra for p T > 1.8 GeV/c within the experimental uncertainties. The measurement of the coalescence parameter B 2 is performed, showing a p T dependence in contrast with the simplest coalescence model, which fails to reproduce also the measured v 2 coefficient. Finally, in addition, the coalescence parameter B 2 and the elliptic flow coefficient in the 20–40% centrality interval are compared with the AMPT model which is able, in its version without string melting, to reproduce the measured v 2 (p T ) and the B 2 (p T ) trend.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗