875 research outputs found
Material Budget Calculation of the new Inner Tracking System, ALICE
The ALICE Collaboration aims at studying the physics of strongly interacting
matter by building up a dedicated heavy-ion detector. The Inner Tracking System
(ITS) is located in the heart of the ALICE Detector surrounding the interaction
point. Now, ALICE has a plan to upgrade the inner tracking system for rare
probes at low transverse momentum. The new ITS composes of seven layers of
silicon pixel sensor on the supporting structure. One goal of the new design is
to reduce the material budget () per layer to 0.3 for inner layers
and 0.8 for middle and outer layers. In this work, we perform the
calculations based on detailed geometry descriptions of different supporting
structures for inner and outer barrel using ALIROOT. Our results show that it
is possible to reduce the material budget of the inner and outer barrel to the
value that we have expected. The manufacturing of such prototypes are also
possible.Comment: 13 pages, 9 figures, regular pape
Poly(hydroxy acids) derived from the self-condensation of hydroxy acids: from polymerization to end-of-life options
[EN] Poly(hydroxy acids) have been gaining increasing attention in the search for novel sustainable materials to replace petrochemical polymers in packaging applications. Poly(hydroxy acids) are polyesters that are obtained using hydroxy acids as the starting materials, which are derived from renewable resources and biowaste. These biopolymers have attracted a lot of attention since some of them will be in the near future competitive in price to polyolefins, show excellent mechanical and barrier properties, and can be potentially recycled by physical and chemical routes. Most of the current poly(hydroxy acids) are mainly prepared by ring-opening polymerization (ROP) of cyclic monomers derived from hydroxy acids. However, their direct polymerization has received much less attention, while one of the advantages of hydroxy acids resides in the presence of an electrophile and a nucleophile in a single molecule that makes them ideal A-B type monomers for self-condensation. This review focuses on the preparation of poly(hydroxy acids) by the self-condensation polymerization of hydroxy acids. Moreover, their end-of-life options are also evaluated considering not only their biodegradability but also their potential to be chemically recycledThe authors thank the European Commission (EC) for financial support through the project SUSPOL-EJDH2020-ITN-2014-642671 and the Spanish Ministry of Science and Innovation (MICI) through the projects RTI2018-097249-B-C21, MAT2017-83373-R, and MAT-2016-78527-P. S. Torres-Giner also acknowledges MICI for his Juan de la Cierva-Incorporacion contract (IJCI-2016-29675) and the financial support received during his stay at the Institute for Polymer Materials (POLYMAT)Gabirondo, E.; Sangroniz, A.; Etxeberria, A.; Torres-Giner, S.; Sardon, H. (2020). Poly(hydroxy acids) derived from the self-condensation of hydroxy acids: from polymerization to end-of-life options. Polymer Chemistry. 11(30):4861-4874. https://doi.org/10.1039/D0PY00088DS48614874113
Enhanced production of multi-strange hadrons in high-multiplicity proton-proton collisions
At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark-gluon plasma (QGP)(1). Such an exotic state of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed(2-6). Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions(7), is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton-proton (pp) collisions(8,9), but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton-proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p-Pb collision results(10,11), indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb-Pb collisions, where a QGP is formed.Peer reviewe
Constraints on jet quenching in p-Pb collisions at root s(NN)=5.02 TeV measured by the event-activity dependence of semi-inclusive hadron-jet distributions
CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high-transverse momentum trigger hadron in p-Pb collisions at root s(NN) = 5.02TeV. Jets are reconstructed from charged-particle tracks using the anti-k(T) algorithm with resolution parameter R = 0.2 and 0.4. A data-driven statistical approach is used to correct the uncorrelated background jet yield. Recoil jet distributions are reported for jet transverse momentum 15 < p(T,jet)(ch) < 50 GeV/c and are compared in various intervals of p-Pb event activity, based on charged-particle multiplicity and zero-degree neutral energy in the forward (Pb-going) direction. The semi-inclusive observable is self-normalized and such comparisons do not require the interpretation of p-Pb event activity in terms of collision geometry, in contrast to inclusive jet observables. These measurements provide new constraints on the magnitude of jet quenching in small systems at the LHC. In p-Pb collisions with high event activity, the average medium-induced out-of-cone energy transport for jets with R = 0.4 and 15 < p(T,jet)(ch) < 50 GeV/c is measured to be less than 0.4 GeV/c at 90% confidence, which is over an order of magnitude smaller than a similar measurement for central Pb-Pb collisions at root s(NN) = 2.76 TeV. Comparison is made to theoretical calculations of jet quenching in small systems, and to inclusive jet measurements in p-Pb collisions selected by event activity at the LHC and in d-Au collisions at RHIC.78395113CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOSem informaçãoSem informaçãoSem informaçãoAgências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig
Inclusive J/ψ production at forward and backward rapidity in p-Pb collisions at √sNN=8.16 TeV
Inclusive J/psi production is studied in p-Pb interactions at a centre-of-mass
energy per nucleon-nucleon collision sqrt(s_NN) = 8.16TeV, using the ALICE detector at the
CERN LHC. The J/psi meson is reconstructed, via its decay to a muon pair, in the centre-of-mass
rapidity intervals 2.03 < ycms < 3.53 and -4.46 < ycms < -2.96, where positive
and negative ycms refer to the p-going and Pb-going direction, respectively. The transverse
momentum coverage is pT < 20 GeV/c. In this paper, ycms- and pT-differential cross
sections for inclusive J/psi production are presented, and the corresponding nuclear modification
factors RpPb are shown. Forward results show a suppression of the J/psi yield with
respect to pp collisions, concentrated in the region pT < 5 GeV/c. At backward rapidity
no significant suppression is observed. The results are compared to previous measurements
by ALICE in p-Pb collisions at sqrt(s_NN) = 5.02TeV and to theoretical calculations. Finally,
the ratios RFB between forward- and backward-ycms RpPb values are shown and discussed
phi-Meson production at forward rapidity in p-Pb collisions at root s(NN)=5.02 TeV and in pp collisions at root s=2.76 TeV
The first study of phi-meson production in p-Pb collisions at forward and backward rapidity, at a nucleonnucleon centre-of-mass energy root s(NN)= 5.02 TeV, has been performed with the ALICE apparatus at the LHC. The phi-mesons have been identified in the dimuon decay channel in the transverse momentum (p(T)) range 1 <p(T) <7GeV/c, both in the p-going (2.03 <y <3.53) and the Pb-going (-4.46 <y <-2.96) directions - where ystands for the rapidity in the nucleon-nucleon centre-of-mass - the integrated luminosity amounting to 5.01 +/- 0.19nb(-1) and 5.81 +/- 0.20nb(-1), respectively, for the two data samples. Differential cross sections as a function of transverse momentum and rapidity are presented. The forward-backward ratio for f-meson production is measured for 2.96Peer reviewe
Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at √sNN=5.02 and 2.76 TeV
Measurements of anisotropic flow coefficients with two- and multi-particle cumulants
for inclusive charged particles in Pb-Pb collisions at sqrt(s_NN) = 5.02 and 2.76TeV
are reported in the pseudorapidity range |eta|< 0.8 and transverse momentum 0.2 < pT <
50 GeV/c. The full data sample collected by the ALICE detector in 2015 (2010), corresponding
to an integrated luminosity of 12.7 (2.0) ub^-1 in the centrality range 0-80%,
is analysed. Flow coefficients up to the sixth flow harmonic (v6) are reported and a detailed
comparison among results at the two energies is carried out. The pT dependence
of anisotropic flow coefficients and its evolution with respect to centrality and harmonic
number n are investigated. An approximate power-law scaling of the form vn(pT) ~ pT^(n/3)
is observed for all flow harmonics at low pT (0.2 < pT < 3 GeV/c). At the same time, the
ratios vn/vm^(n/m) are observed to be essentially independent of pT for most centralities up to
about pT = 10 GeV/c. Analysing the differences among higher-order cumulants of elliptic flow (v2),
which have different sensitivities to flow fluctuations, a measurement of the standardised
skewness of the event-by-event v2 distribution P(v2) is reported and constraints
on its higher moments are provided. The Elliptic Power distribution is used to parametrise
P(v2), extracting its parameters from fits to cumulants. The measurements are compared
to different model predictions in order to discriminate among initial-state models and to
constrain the temperature dependence of the shear viscosity to entropy-density ratio
First measurement of Ξc0 production in pp collisions at s=7 TeV
The production of the charm-strange baryon Csi0c is measured for the first time at the LHC via its
semileptonic decay into e+Csi-νe in pp collisions at sqrt(s) = 7 TeV with the ALICE detector. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 1 < pT < 8 GeV/c at mid-rapidity, |y| < 0.5. The transverse momentum dependence of the Csi0c baryon production relative to the D0 meson production is compared to predictions of event generators with various tunes of the hadronisation mechanism, which are found to underestimate the measured cross- section ratio.The production of the charm-strange baryon Csi0c is measured for the first time at the LHC via its
semileptonic decay into e+Csi-νe in pp collisions at sqrt(s) = 7 TeV with the ALICE detector. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 1 < pT < 8 GeV/c at mid-rapidity, |y| < 0.5. The transverse momentum dependence of the Csi0c baryon production relative to the D0 meson production is compared to predictions of event generators with various tunes of the hadronisation mechanism, which are found to underestimate the measured cross- section ratio
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