A multi-step setup for heavy-flavor studies in high-energy nucleus-nucleus (
AA
) collisions—addressing within a comprehensive framework the initial
production, the propagation in the hot medium ...until decoupling and the final hadronization and decays—is presented. The initial hard production of
pairs is simulated using the POWHEG pQCD event generator, interfaced with the PYTHIA parton shower. Outcomes of the calculations are compared to experimental data in
pp
collisions and are used as a validated benchmark for the study of medium effects. In the
AA
case, the propagation of the heavy quarks in the medium is described in a framework provided by the relativistic Langevin equation. For the latter, different choices of transport coefficients are explored (either provided by a perturbative calculation or extracted from lattice-QCD simulations) and the corresponding numerical results are compared to experimental data from RHIC and the LHC. In particular, outcomes for the nuclear modification factor
R
AA
and for the elliptic flow
v
2
of
D
/
B
mesons, heavy-flavor electrons and non-prompt
J
/
ψ
’s are displayed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Silicon Drift Detector of the ALICE experiment Sitta, M.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
The calibration and performance of the Silicon Drift Detector of the ALICE experiment will be presented. In particular the monitoring of the drift speed and the charge calibration with cosmic muons ...will be explained.
The aim of the ALICE Collaboration is to study the physics of strongly interacting matter by using the experimental results from a dedicated heavy-ion detector. The Inner Tracking System (ITS) is ...located at the heart of the ALICE detector surrounding the interaction point. Currently, ALICE is planning to upgrade the ITS for rare probes at low transverse momenta. The new ITS comprises seven layers of silicon pixel sensors on the supporting structure. One goal of the new design is to reduce the material budget (X/X0) per layer to 0.3% for the inner layers and 0.8% for the middle and outer layers. In this work, we perform simulations based on detailed geometrical descriptions of different supporting structures for the inner and outer barrels by using ALIROOT. Our results indicate that it is possible to reduce the material budget of the inner and outer barrels to the expected value. Manufacturing of such prototypes is also possible.
Aim
To evaluate the ability of the Short Physical Performance Battery (SPPB) for predicting 1-year adverse outcomes of acutely ill older outpatients.
Methods
Prospective study with 512 acutely ill ...older outpatients (79.4±8.3 years, 63% female) in an acute care day hospital. The SPPB was administered at admission. Participants were classified as low (0–4 points), intermediate (5–8 points), or high (9–12 points) performance. Primary outcomes were new dependence in basic activities of daily living (ADL), hospitalization, and death at 1 year. Cox models tested whether the SPPB predicted outcomes after adjustment for sociodemographic factors, comorbidities and well-known geriatric conditions. We also estimated whether the chair-stand and balance tests improve the SPPB’s ability to identify patients at high risk of adverse outcomes.
Results
Patients with intermediate or low SPPB performance were at higher risk of 1-year new ADL dependence (32% vs 13%: adjusted hazard ratio aHR=2.00; 95%CI=1.18–3.37; 58% vs 13%: aHR=3.40; 95%CI=2.00–5.85, respectively), hospitalization (43% vs 29%: aHR=1.56; 95%CI=1.04–2.33; 44% vs 29%: aHR=1.80; 95%CI=1.15–2.82), and death (18% vs 6%: aHR=2.54; 95%CI=1.17–5.53; 21% vs 6%: aHR=2.70; 95%CI=1.17–6.21). Use of all three components (versus gait speed alone) improved predictions of new ADL dependence (Harrell’s C=0.73 vs 0.70;P=0.01), hospitalization (Harrell’s C=0.60 vs 0.57;P=0.04), and death (Harrell’s C=0.67 vs 0.62;P=0.04).
Conclusions
The SPPB is as a powerful tool for identifying acutely ill older outpatients at high-risk of adverse outcomes. The combination of the three components of the SPPB resulted in better predictive performance than gait speed alone.
Abstract
The Zero Degree Calorimeters (ZDC) were designed to provide the measurement of the event geometry and luminosity in heavy-ion operation. The readout system was redesigned in order to operate ...in continuous mode without dead time at 2.5 MHz event rate. The new acquisition chain is based on a commercial 12 bit digitizer with a sampling rate of about 1 GSps, assembled on an FPGA Mezzanine Card. The signals produced by the 26 ZDC channels are digitized, and samples are processed through an FPGA to extract information such as timing, baseline average estimation and luminosity.
We present a new measurement of $J/\psi$ production in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental ...conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that the ($J/\psi$)/Drell-Yan cross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that the ($J/\psi$)/Drell-Yan cross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Introduction: Charged Particle Therapy plays a key role in the treatment of deep-seated tumours, because of the advantageous energy deposition culminating in the Bragg peak. However, knowledge of the ...dose delivered in the entrance channel is limited by the lack of data on the beam and fragmentation of the target. Methods: The FOOT experiment has been designed to measure the cross sections of the nuclear fragmentation of projectile and target with two different detectors: an electronic setup for the identification of Z ≥ 3 fragments and a nuclear emulsion spectrometer for Z ≤ 3 fragments. In this paper, we analyze the data taken by exposing four nuclear emulsion spectrometers, with C and C 2 H 4 targets, to 200 MeV/n and 400 MeV/n oxygen beams at GSI Helmholtzzentrum für Schwerionenforschung (Darmstadt, Germany), and we report the charge identification of produced fragments based on the controlled fading induced on nuclear emulsion films. Results: The goal of identifying fragments as heavy as lithium has been achieved. Discussion: The results will contribute to a better understanding of the nuclear fragmentation process in charged particle therapy and have implications for refining treatment planning in the presence of deep-seated tumors.
We report a new measurement of J/ψ, ψ′ and Drell–Yan cross-sections, in the kinematical domain -0.425<ycm<0.575 and -0.5<cosθCS<0.5, performed at the CERN-SPS using 400 GeV/c incident protons on Be, ...Al, Cu, Ag, W and Pb targets. The dependence of the charmonia production cross-sections on the size of the target nucleus allows to quantify the so-called normal nuclear absorption. In the framework of the Glauber model, this new measurement is combined with results previously obtained with the same apparatus, under different experimental conditions, and leads to a precise determination of the J/ψ and ψ′ absorption cross-sections in the surrounding nuclear matter.
A multi-step setup for heavy-flavour studies in high-energy nucleus–nucleus collisions is presented. The initial hard production of QQ¯ pairs is simulated with the POWHEG pQCD event generator, ...interfaced with the PYTHIA parton shower. In a nucleus–nucleus collision the propagation of the heavy quarks in the medium is described through the relativistic Langevin equation. The numerical results are compared to experimental data from the RHIC and the LHC. In particular we show the comparisons of the nuclear modification factor of D-mesons, non-prompt J/ψ's and heavy-flavour electrons. Furthermore, first results on azimuthal correlations of heavy quark pair and open charm/beauty meson pairs are presented.
Observational studies suggest that male circumcision may provide protection against HIV-1 infection. A randomized, controlled intervention trial was conducted in a general population of South Africa ...to test this hypothesis.
A total of 3,274 uncircumcised men, aged 18-24 y, were randomized to a control or an intervention group with follow-up visits at months 3, 12, and 21. Male circumcision was offered to the intervention group immediately after randomization and to the control group at the end of the follow-up. The grouped censored data were analyzed in intention-to-treat, univariate and multivariate, analyses, using piecewise exponential, proportional hazards models. Rate ratios (RR) of HIV incidence were determined with 95% CI. Protection against HIV infection was calculated as 1 - RR. The trial was stopped at the interim analysis, and the mean (interquartile range) follow-up was 18.1 mo (13.0-21.0) when the data were analyzed. There were 20 HIV infections (incidence rate = 0.85 per 100 person-years) in the intervention group and 49 (2.1 per 100 person-years) in the control group, corresponding to an RR of 0.40 (95% CI: 0.24%-0.68%; p < 0.001). This RR corresponds to a protection of 60% (95% CI: 32%-76%). When controlling for behavioural factors, including sexual behaviour that increased slightly in the intervention group, condom use, and health-seeking behaviour, the protection was of 61% (95% CI: 34%-77%).
Male circumcision provides a degree of protection against acquiring HIV infection, equivalent to what a vaccine of high efficacy would have achieved. Male circumcision may provide an important way of reducing the spread of HIV infection in sub-Saharan Africa. (Preliminary and partial results were presented at the International AIDS Society 2005 Conference, on 26 July 2005, in Rio de Janeiro, Brazil.).
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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