2,329 research outputs found
Study of strange particle production in pp collisions with the ALICE detector
ALICE is well suited for strange particles production studies since it has
very good reconstruction capabilities in the low transverse momentum ()
region and it also allows to extend the identification up to quite high
. Charged strange mesons (\kp, \km,) are reconstructed via energy
loss measurements whereas neutral strange mesons (\ks) and strange hyperons
(\lam, , ) are identified via vertex reconstruction. All these
particles carry important information: first, the measurement of production
yields and the particle ratio within the statistical models can help to
understand the medium created and secondly the dynamics at intermediate
investigated via the baryon over meson ratio (\lam / \ks) allows a better
understanding of the hadronization mechanisms and of the underlying event
processes. We present these two aspects of the strange particles analysis in pp
collisions using simulated data.Comment: Proceeding SQM (2009), 5 figures, 6 page
Measurement of , K, p transverse momentum spectra with ALICE in proton-proton collisions at 0.9 and 7 TeV
Results of the measurement of the , K, p transverse momentum
() spectra at mid-rapidity in proton-proton collisions at
TeV are presented. Particle identification was performed using
the energy loss signal in the Inner Tracking System (ITS) and the Time
Projection Chamber (TPC), while information from the Time-of-Flight (TOF)
detector was used to identify particles at higher transverse momentum. From the
spectra at TeV the mean transverse momentum ()
and particle ratios were extracted and compared to results obtained for
collisions at TeV and lower energies.Comment: Quark Matter 2011 proceeding
K0s and \Lambda\ production in Pb--Pb collisions with the ALICE experiment
We present the study of K0s and Lambda production performed with the ALICE
experiment at the LHC in Pb--Pb collisions at \sqrt{s_NN}=2.76 TeV and pp
collisions at \sqrt{s}=0.9 and 7 TeV. The K0s and Lambda particles are
reconstructed via their V0 decay topology allowing their identification up to
high transverse momenta. The corresponding baryon/meson ratios as a function of
transverse momentum are extracted for Pb--Pb collisions in centrality bins and
in the transverse momentum range from 1 to 6 GeV/c. They are also compared with
those measured in pp events at the LHC energies of 0.9 and 7 TeV as well as in
Au--Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV from RHIC.Comment: 4 pages, 4 figures, proceedings of Quark Matter 2011 (May 23rd-28th
2011, Annecy, France
A comprehensive study of rate capability in Multi-Wire Proportional Chambers
Systematic measurements on the rate capability of thin MWPCs operated in
Xenon, Argon and Neon mixtures using CO2 as UV-quencher are presented. A good
agreement between data and existing models has been found, allowing us to
present the rate capability of MWPCs in a comprehensive way and ultimately
connect it with the mobilities of the drifting ions.Comment: 29 pages, 18 figure
Testing production scenarios for (anti-)(hyper-)nuclei with multiplicity-dependent measurements at the Lhcâ
The production of light anti- and hyper-nuclei provides unique observables to characterise the system created in high-energy protonâproton (pp), protonânucleus (pA) and nucleusânucleus (AA) collisions. In particular, nuclei and hyper-nuclei are special objects with respect to non-composite hadrons (such as pions, kaons, protons, etc.), because their size is comparable to a fraction or the whole system created in the collision. Their formation is typically described within the framework of coalescence and thermal-statistical production models. In order to distinguish between the two production scenarios, we propose to measure the coalescence parameter BA for different anti- and hyper-nuclei (that differ by mass, size and internal wave function) as a function of the size of the particle emitting source. The latter can be controlled by performing systematic measurements of light anti- and hyper-nuclei in different collision systems (pp, pA, AA) and as a function of the multiplicity of particles created in the collision. While it is often argued that the coalescence and the thermal model approach give very similar predictions for the production of light nuclei in heavy-ion collisions, our study shows that large differences can be expected for hyper-nuclei with extended wave functions, as the hyper-triton. We compare the model predictions with data from the ALICE experiment and we discuss perspectives for future measurements with the upgraded detectors during the High-Luminosity LHC phase in the next decade
Testing production scenarios for (anti-)(hyper-)nuclei and exotica at energies available at the CERN Large Hadron Collider
We present a detailed comparison of coalescence and thermal-statistical models for the production of (anti-) (hyper-)nuclei in high-energy collisions. For the first time, such a study is carried out as a function of the size of the object relative to the size of the particle emitting source. Our study reveals large differences between the two scenarios for the production of objects with extended wave functions. While both models give similar predictions and show similar agreement with experimental data for (anti-)deuterons and (anti-)He3 nuclei, they largely differ in their description of (anti-)hypertriton production. We propose to address experimentally the comparison of the production models by measuring the coalescence parameter systematically for different (anti-)(hyper-)nuclei in different collision systems and differentially in multiplicity. Such measurements are feasible with the current and upgraded Large Hadron Collider experiments. Our findings highlight the unique potential of ultrarelativistic heavy-ion collisions as a laboratory to clarify the internal structure of exotic QCD objects and can serve as a basis for more refined calculations in the future
Measurement of the nuclear modification factor of electrons from heavy-flavour decays at mid-rapidity in Pb-Pb collisions at = 2.76 TeV with ALICE
We present results on inclusive electrons for 1.5 6 GeV/
in {Pb-Pb} collisions at = 2.76 TeV measured with ALICE at
the LHC and compare these to a cocktail of background electron sources. The
excess of electrons beyond the cocktail at high momenta ({ 3.5
GeV/}) is attributed to electrons from heavy-flavour decays. The
corresponding nuclear modification factor indicates heavy-flavour suppression
by a factor of 1.5-4.Comment: 4 pages; 4 figures; QM 2011 proceeding
Production of nuclei and antinuclei in pp and Pb-Pb collisions with ALICE at the LHC
We present first results on the production of nuclei and antinuclei such as
(anti)deuterons, (anti)tritons, (anti)3He and (anti)4He in pp collisions at
\s = 7 TeV and Pb-Pb collisions at \sNN = 2.76 TeV. These particles are
identified using their energy loss (dE/dx) information in the Time Projection
Chamber of the ALICE experiment. The Inner Tracking System gives a precise
determination of the event vertex, by which primary and secondary particles are
separated. The high statistics of over 360 million events for pp and 16 million
events for Pb-Pb collisions give a significant number of light nuclei and
antinuclei (Pb-Pb collisions: \sim30,000 anti-deuterons() and \sim4
anti-alpha()). The predictions of various particle ratios from the
THERMUS model is also discussed.Comment: 4 pages, 5 figures, parallel talk at Quark Matter 2011, May 23rd-28th
2011, Annecy, Franc
Examination of coalescence as the origin of nuclei in hadronic collisions
The origin of weakly bound nuclear clusters in hadronic collisions is a key question to be addressed by heavy-ion collision (HIC) experiments. The measured yields of clusters are approximately consistent with expectations from phenomenological statistical hadronization models (SHMs), but a theoretical understanding of the dynamics of cluster formation prior to kinetic freeze-out is lacking. The competing model is nuclear coalescence, which attributes cluster formation to the effect of final state interactions (FSI) during the propagation of the nuclei from kinetic freeze-out to the observer. This phenomenon is closely related to the effect of FSI in imprinting femtoscopic correlations between continuum pairs of particles at small relative momentum difference. We give a concise theoretical derivation of the coalescence-correlation relation, predicting nuclear cluster spectra from femtoscopic measurements. We review the fact that coalescence derives from a relativistic Bethe-Salpeter equation, and recall how effective quantum mechanics controls the dynamics of cluster particles that are nonrelativistic in the cluster center-of-mass frame. We demonstrate that the coalescence-correlation relation is roughly consistent with the observed cluster spectra in systems ranging from PbPb to pPb and pp collisions. Paying special attention to nuclear wave functions, we derive the coalescence prediction for the hypertriton and show that it, too, is roughly consistent with the data. Our work motivates a combined experimental programme addressing femtoscopy and cluster production under a unified framework. Upcoming pp, pPb, and peripheral PbPb data analyzed within such a program could stringently test coalescence as the origin of clusters
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