2,712 research outputs found
Nuclear matter distributions in the neutron-rich carbon isotopes 14−17C from intermediate-energy proton elastic scattering in inverse kinematics
No full textThe absolute differential cross sections for small-angle proton elastic scattering off the nuclei 12,14−17C have been measured in inverse kinematics at energies near 700 MeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served simultaneously as a gas target and a detector for the recoil protons. The projectile scattering angles were measured with multi-wire tracking detectors. The radial nuclear matter density distributions and the root-mean-square nuclear matter radii were deduced from the measured cross sections using the Glauber multiple-scattering theory. A possible neutron halo structure in 15C, 16C and 17C is discussed. The obtained data show evidence for a halo structure in the 15C nucleus
Nuclear-matter distribution in the proton-rich nuclei 7Be and 8B from intermediate energy proton elastic scattering in inverse kinematics
No full textAbsolute differential cross sections for elastic p7Be and p8B small-angle scattering were measured in inverse kinematics at an energy of 0.7 GeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR was used as an active target to detect the recoil protons. The projectile tracking and isotope identification were performed with multi-wire proportional chambers and scintillation detectors. The measured cross sections were analysed using the Glauber multiple-scattering theory. The root-mean-square (rms) nuclear matter radii Rm=2.42(4) fm for 7Be and Rm=2.58(6) fm for 8B were obtained. The radial density distribution deduced for 8B exhibits a proton halo structure with the rms halo radius Rh=4.24(25) fm. A comparison of the deduced experimental radii is displayed with existing experimental and theoretical data
Measuring (KSK +/-)-K-0 interactions using Pb-Pb collisions at root S-NN=2.76 TeV
No full textWe present the first ever measurements of femtoscopic correlations between the K-S(0) and K-+/- particles. The analysis was performed on the data from Pb-Pb collisions at root S-NN = 2.76 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding via the a(0)(980) resonance. The extracted kaon source radius and correlation strength parameters for (KSK-)-K-0 are found to be equal within the experimental uncertainties to those for (KSK+)-K-0. Comparing the results of the present study with those from published identical-kaon femtoscopic studies by ALICE, mass and coupling parameters for the a(0) resonance are tested. Our results are also compatible with the interpretation of the a(0) having a tetraquark structure instead of that of a diquark. (c) 2017 The Author. Published by Elsevier B.V
First Observation of an Attractive Interaction between a Proton and a Cascade Baryon
No full textThis Letter presents the first experimental observation of the attractive strong interaction between a
proton and a multistrange baryon (hyperon) Ξ−. The result is extracted from two-particle correlations of
− ̄ þ pffiffiffiffiffiffiffi
⊕ p ̄ -Ξ pairs measured in p-Pb collisions at sNN 1⁄4 5.02 TeV at the LHC with ALICE.
combined p-Ξ
The measured correlation function is compared with the prediction obtained assuming only an attractive Coulomb interaction and a standard deviation in the range [3.6, 5.3] is found. Since the measured p-Ξ− ⊕ p ̄-Ξ ̄þ correlation is significantly enhanced with respect to the Coulomb prediction, the presence of an additional, strong, attractive interaction is evident. The data are compatible with recent lattice calculations by the HAL-QCD Collaboration, with a standard deviation in the range [1.8, 3.7]. The lattice potential predicts a shallow repulsive Ξ− interaction within pure neutron matter and this implies stiffer equations of state for neutron-rich matter including hyperons. Implications of the strong interaction for the modeling of neutron stars are discussed
Measurement of the production of high-p(T) electrons from heavy-flavour hadron decays in Pb-Pb collisions at root s(NN)=2.76 TeV
No full textElectrons from heavy-flavour hadron decays (charm and beauty) were measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass of energy root s(NN) = 2.76 TeV. The transverse momentum (pT) differential production yields at mid-rapidity were used to calculate the nuclear modification factor R-AA in the interval 3 < p(T) < 18 GeV/c. The R-AA shows a strong suppression compared to binary scaling of pp collisions at the same energy (up to a factor of 4) in the 10% most central Pb-Pb collisions. There is a centrality trend of suppression, and a weaker suppression (down to a factor of 2) in semi-peripheral (50-80%) collisions is observed. The suppression of electrons in this broad p(T) interval indicates that both charm and beauty quarks lose energy when they traverse the hot medium formed in Pb-Pb collisions at LHC. (C) 2017 The Author. Published by Elsevier B.V
The Front-End Electronics for the Tracking System of the ALICE Muon Spectrometer
No full textA review of the two generations of front-end electronics for the muon spectrometer of the ALICE experiment at the Large Hadron Collider is presented. The basic elements of the front-end electronics are application-specific integrated circuits that are used in 1.1 × 10 measuring channels and devices for communication with the data-acquisition system. The first generation of the electronics operates in the trigger mode and is characterized by an input throughput of 3 × 10 events/s at an output data rate of 3.2 Gbit/s. The second generation is designed to operate under conditions of a high luminosity of the collider at input count rates of up to 10 events/s. Signal processing is performed in the continuous readout mode. The communication devices with the data-acquisition system use application-specific chips that provide optical communication with a data transfer rate of 0.8 Tbit/s
Investigating correlated fluctuations of conserved charges with net-A fluctuations in Pb-Pb collisions at ALICE
No full textEvent-by-event fluctuations of conserved charges such as electric
charge, strangeness, and baryon number - in ultrarelativistic heavy-ion
collisions provide insight into the properties of the quark-gluon plasma
and the QCD phase diagram. They can be related to the higher moments of
the multiplicity distributions of identified particles, such as the A
baryon which carries both strangeness and baryon number and is thus of
particular interest. We present the first measurement of net-A
fluctuations in Pb-Pb collisions at root s(NN)=5.02 TeV as a function of
centrality and the pseudorapidity acceptance of the measurement. The
results are compared to expectations of the effects of global baryon
number conservation as well as to predictions from the HIJING Monte
Carlo event generator. In this analysis the Identity Method is applied
in a novel way to account for the combinatoric background in the
invariant mass distribution
Investigating correlated fluctuations of conserved charges with net-A fluctuations in Pb-Pb collisions at ALICE
No full textEvent-by-event fluctuations of conserved charges such as electric charge, strangeness, and baryon number - in ultrarelativistic heavy-ion collisions provide insight into the properties of the quark-gluon plasma and the QCD phase diagram. They can be related to the higher moments of the multiplicity distributions of identified particles, such as the A baryon which carries both strangeness and baryon number and is thus of particular interest. We present the first measurement of net-A fluctuations in Pb-Pb collisions at root s(NN)=5.02 TeV as a function of centrality and the pseudorapidity acceptance of the measurement. The results are compared to expectations of the effects of global baryon number conservation as well as to predictions from the HIJING Monte Carlo event generator. In this analysis the Identity Method is applied in a novel way to account for the combinatoric background in the invariant mass distribution
Measurements of anisotropic flow and flow fluctuations in Xe-Xe and Pb-Pb collisions with ALICE
No full textAnisotropic flow is a key observable to characterise the system created
in heavy-ion collisions, as it is sensitive to the system's initial
state, transport properties, the equation of state and freeze-out
conditions. In these proceedings we present the anisotropic flow
coefficients of inclusive charged particles in Pb-Pb collisions at root
s(NN) = 2.76 and 5.02 TeV, and in Xe-Xe collisions at root s(NN) = 5.44
TeV. The results are reported for a wide range of particle transverse
momentum within the pseudo-rapidity range vertical bar eta vertical bar
< 0.8 at different collision centralities. The energy and system
dependence are found to place strong constraints on the temperature
dependence of eta/s and the modeling of the initial state, respectively.
We also present detailed studies of flow fluctuations in heavy-ion
collisions, in order to precisely characterise the underlying flow
probability density function. We find evidence of non-Bessel-Gaussian
fluctuations and discuss the origin of this observation
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