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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Mid-rapidity anti-baryon to baryon ratios in pp collisions at $\sqrt{s} = 0.9,\ 2.76\mbox{ and }7\mbox{ TeV}$ measured by ALICE

The ratios of yields of anti-baryons to baryons probes the mechanisms of baryon-number transport. Results for \(\overline{\mathrm {p}}/{\mathrm{p}}\) , \(\overline{\Lambda}/{\Lambda}\) , \({{\overline{\Xi}}^{+}}/{\Xi ^{-}}\) and \({{\overline{\Omega}}^{+}}/{\Omega^{-}}\) in pp collisions at \(\sqrt{s} = 0.9,\ 2.76\mbox{ and }7\mbox{ TeV}\) , measured with the ALICE detector at the LHC, are reported. Within the experimental uncertainties and ranges covered by our measurement, these ratios are independent of rapidity, transverse momentum and multiplicity for all measured energies. The results are compared to expectations from event generators, such as PYTHIA and HIJING/B, that are used to model the particle production in pp collisions. The energy dependence of \(\overline{\mathrm{p}}/{\mathrm{p}}\) , \(\overline {\Lambda}/{\Lambda}\) , \({{\overline{\Xi}}^{+}}/{\Xi^{-}}\) and \({{\overline{\Omega}}^{+}}/{\Omega^{-}}\) , reaching values compatible with unity for \(\sqrt{s} = 7\mbox{ TeV}\) , complement the earlier \(\overline{\mathrm{p}}/{\mathrm{p}}\) measurement of ALICE. These dependencies can be described by exchanges with the Regge-trajectory intercept of \(\alpha_{\rm{J}} \approx0.5\) , which are suppressed with increasing rapidity interval Δ y . Any significant contribution of an exchange not suppressed at large Δ y (reached at LHC energies) is disfavoured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Measurement of ${{\mathrm{D}}^0}$, ${{\mathrm{D}}^+}$, ${{\mathrm{D}}^{*+}}$ and ${{\mathrm{D}}^+_{\mathrm{s}}}$ production in pp collisions at ${\sqrt{{\textit{s}}}~=~5.02~{\text {TeV}}}$ with ALICE

The measurements of the production of prompt D 0 , D + , D *+ , and D$_s^+$ mesons in proton–proton (pp) collisions at $\sqrt{s}$=5.02 TeV with the ALICE detector at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity (|y| < 0.5) via their hadronic decay channels D 0 → K - $π$ + , D + → K - $π$ + $π$ + , D *+ → D 0 $π$ + → K - $π$ + $π$ + , D$_s^+$ → Φ$π$ + → K + K - $π$ + , and their charge conjugates. The production cross sections were measured in the transverse momentum interval 0 < $p$T < 36 GeV/$c$ for D 0 , 1 < $p$T < 36 GeV/$c$ for D + and D *+ , and in 2 < $p$T < 24 GeV/$c$ for D$_s^+$ mesons. Thanks to the higher integrated luminosity, an analysis in finer $p$T bins with respect to the previous measurements at $\sqrt{s}$ = 7 TeV was performed, allowing for a more detailed description of the cross-section $p$T shape. The measured $p$T differential production cross sections are compared to the results at √ s = 7 TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at $\sqrt{s}$ = 5.02 TeV. This measurement will allow for a more accurate determination of the nuclear modification factor in p–Pb and Pb–Pb collisions performed at the same nucleon– nucleon centre-of-mass energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Characterization of the initial state and medium properties of heavy-ion collisions at ALICE

This report summarizes the key achievements from my "Characterization of the initial state and medium properties of heavy-ion collisions at ALICE" award. This report summarizes the key achievements from DOE award, which started February 1st 2015, and ended January 31st 2018. The award funded experimental research into relativistic heavy-ion collisions at two facilities: The ALICE detector at the Large Hadron Collider (LHC) at CERN, and the STAR detector at Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Relativistic heavy-ion collisions aim to create the Quark Gluon Plasma (QGP) is a unique state where the building blocks of nuclear matter, quarks and gluons, melt and move freely over the volume of the nucleus. It is believed that the universe temporarily existed in such a state shortly after the big bang, where the temperatures needed for this transition are roughly 100,000 times bigger than the temperature at the center of the Sun. Experimental data collected over the past decade at RHIC have provided evidence that the QGP has been created in the laboratory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1992

The ALICE instrument and the measured cosmic ray elemental abundances

A Large Isotopic Composition Experiment (ALICE) is a balloon-borne spectrometer which can determine the elemental and isotopic composition of galactic cosmic rays with energies near 1 GeV/nucleon. ALICE was flown from Prince Albert, Canada in August 1987, and remained at float altitude (120,000 feet) for 14.7 hours. In this paper, we describe the experimental methods and analysis which will be used for subsequent isotopic analysis. We obtained very precise charge resolution over the entire designed range: 0.10 and 0.16 charge units at neon and iron, respectively. Results on the galactic cosmic ray abundances and absolute fluxes of the elements from neon through nickel are reported.

Esposito, J. A.↗
DOE OSTI2019

Stellar Occultation by Comet 67P/Churyumov–Gerasimenko Observed with Rosetta's Alice Far-ultraviolet Spectrograph

Following our previous detection of ubiquitous H{sub 2}O and O{sub 2} absorption against the far-ultraviolet continuum of stars located near the nucleus of Comet 67P/Churyumov–Gerasimenko, we present a serendipitously observed stellar occultation that occurred on 2015 September 13, approximately one month after the comet’s perihelion passage. The occultation appears in two consecutive 10-minute spectral images obtained by Alice, Rosetta’s ultraviolet (700–2100 Å) spectrograph, both of which show H{sub 2}O absorption with column density >10{sup 17.5} cm{sup −2} and significant O{sub 2} absorption (O{sub 2}/H{sub 2}O ≈ 5%–10%). Because the projected distance from the star to the nucleus changes between exposures, our ability to study the H{sub 2}O column density profile near the nucleus (impact parameters <1 km) is unmatched by our previous observations. We find that the H{sub 2}O and O{sub 2} column densities decrease with increasing impact parameter, in accordance with expectations, but the O{sub 2} column decreases ∼3 times more quickly than H{sub 2}O. When combined with previously published results from stellar appulses, we conclude that the O{sub 2} and H{sub 2}O column densities are highly correlated, and O{sub 2}/H{sub 2}O decreases with the increasing H{sub 2}O column.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Measurement of ψ (2S) production as a function of charged-particle pseudorapidity density in pp collisions at $ \sqrt{s}$ = 13 TeV and p–Pb collisions at $ \sqrt{s_{\textrm{NN}}}$ = 8.16 TeV with ALICE at the LHC

Production of inclusive charmonia in pp collisions at center-of-mass energy of $ \sqrt{s}$= 13 TeV and p–Pb collisions at center-of-mass energy per nucleon pair of $ \sqrt{s_{\textrm{NN}}}$ = 8.16 TeV is studied as a function of charged-particle pseudorapidity density with ALICE. Ground and excited charmonium states (J/ψ, ψ(2S)) are measured from their dimuon decays in the interval of rapidity in the center-of-mass frame 2.5 < y cms < 4.0 for pp collisions, and 2.03 < y cms < 3.53 and –4.46 < y cms < –2.96 for p–Pb collisions. The charged-particle pseudorapidity density is measured around midrapidity (|η| < 1.0). In pp collisions, the measured charged-particle multiplicity extends to about six times the average value, while in p-Pb collisions at forward (backward) rapidity a multiplicity corresponding to about three (four) times the average is reached. The ψ(2S) yield increases with the charged-particle pseudorapidity density. The ratio of ψ(2S) over J/ψ yield does not show a significant multiplicity dependence in either colliding system, suggesting a similar behavior of J/ψ and ψ(2S) yields with respect to charged-particle pseudorapidity density. Results for the ψ(2S) yield and its ratio with respect to J/ψ agree with available model calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Study of $\langle {p}_{\text{T}}\rangle$ and its higher moments, and extraction of the speed of sound in Pb-Pb collisions with ALICE

Ultrarelativistic heavy-ion collisions produce a state of hot and dense strongly interacting QCD matter called quark-gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultracentral collisions is mostly constant, while its total entropy can vary significantly due to quantum fluctuations, leading to variations in the temperature of the system. Exploiting this unique feature of ultracentral collisions allows for the interpretation of the correlation of the mean transverse momentum ($\langle$p T $\rangle$) of produced charged hadrons and the number of charged hadrons as a measure for the speed of sound, c s . This speed is related to the rate at which compression waves travel in the QGP and is determined by fitting the relative increase in $\langle$p T $\rangle$ with respect to the relative change in the average charged-particle density ($\langle$dN ch /dη$\rangle$) measured at mid-rapidity. This study reports the event-average $\langle$p T $\rangle$ of charged particles as well as the variance, skewness, and kurtosis of the event-by-event transverse momentum per charged particle ([p T ]) distribution in ultracentral Pb-Pb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are used to select ultracentral collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region used to perform the measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum is tested. The measured c$^{2}_{s}$ is found to strongly depend on the exploited centrality estimator and ranges between 0.1146±0.0028 (stat.)±0.0065 (syst.) and 0.4374±0.0006 (stat.)±0.0184 (syst.) in natural units. The self-normalized variance shows a steep decrease towards ultracentral collisions, while the self-normalized skewness variables show a maximum, followed by a fast decrease. These non-Gaussian features are understood in terms of the vanishing of the impact-parameter fluctuations contributing to the event-to-event [p T ] distribution.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

System size and flavour dependence of chemical freeze-out temperatures in ALICE data from pp, pPb and PbPb collisions at LHC energies

We present the system size and flavour dependence of the chemical freeze-out temperature (T ch ) at vanishing baryo-chemical potential calculated via thermal fits to experimental yields for several multiplicity classes in pp, pPb and PbPb collisions measured by ALICE. Using the Thermal-FIST Hadron Resonance Gas model package, we compare the quality of fits across various treatments of strangeness conservation under different freeze-out conditions as a function of the charged particle multiplicity density $\langle$dN ch /d η $\rangle$. Additionally, we examine how the anti-hadron to pion yield ratios of light and strange baryons, as well as the φ meson, evolve within a flavour-dependent model. Through a unique twotemperature chemical freeze-out approach, we show that flavour dependence of T ch in a Strangeness Canonical Ensemble leads to a natural explanation of strangeness enhancement from small to large systems at LHC energies without requiring any non-equilibrium particle production at small $\langle$dN ch /d η $\rangle$.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Electron-hadron correlations in pp collisions at {radical}(s) = 2.76TeV with the ALICE experiment

In this work we are studying the relative beauty to charm production in pp collisions at {radical}(s) = 2.76TeV, through correlations between electrons from heavy-flavour decay and charged hadrons, with the ALICE detector at the LHC. This study represents a baseline for the analysis in heavy-ion collisions where heavy flavour production is a powerful tool to study the Quark Gluon Plasma (QGP).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Central diffraction in proton-proton collisions at {radical}(s) = 7TeV with ALICE at LHC

A double-gap topology is used for filtering central-diffractive events from a protonproton minimum-bias data sample at a centre-of-mass energy Central diffraction in proton-proton collisions at {radical}(s) = 7TeV. This topology is defined by particle activity in the ALICE central barrel and absence of particle activity outside. The fraction of events satisfying the double-gap requirement R{sub DG} is found to be 7.63{+-}0.02(st at.){+-}0.87(syst.) Multiplication-Sign 10{sup -4}. The background of this double-gap fraction is estimated by studying the contributions of non-diffractive, single-and double-diffractive dissociation processes as modelled by Monte Carlo event generators, and is found to be about 10%.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Neutral meson production in pp and Pb-Pb collisions at the LHC with ALICE

The first measurements of the invariant differential cross sections of inclusive {pi}{sup 0} and {eta} meson production with ALICE are presented for pp collisions at {radical}(s) = 0.9 and 7 TeV. Next-to-Leading Order perturbative QCD calculations overestimate the data at {radical}(s) = 7TeV, but are consistent with the {pi}{sup 0} spectrum at {radical}(s) = 0.9TeV and with the measured {pi}{sup 0}/{eta} cross section ratio at {radical}(s) = 7TeV. The nuclear modification factors (R{sub AA}) of {pi}{sup 0} production at different centralities show a strong suppression with respect to pp collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Elliptic azimuthal anisotropy of heavy-flavour decay electrons in Pb-Pb collisions at √(S{sub NN}) = 2.76 TeV measured with ALICE

In this paper, we present the ALICE results on the elliptic azimuthal anisotropy of heavy-flavour decay electrons in 20-40% central Pb-Pb collisions at √(S{sub NN}) = 2.76 TeV. Heavy quarks are produced in the early stages of the collision and they interact with the hot and dense color-deconfined medium created in heavy-ion collisions at high energies, the Quark-Gluon Plasma (QGP). Measurements of the elliptic azimuthal anisotropy of heavy-flavour decay electrons in non-central collisions can be used to investigate the degree of thermalization and energy loss of heavy quarks within the QGP. Theoretical predictions of heavy-quark transport in the medium are compared with the measurement.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Recent COMPASS results and future prospects for ALICE

The COMPASS Collaboration has accumulated the world’s highest statistics on the reaction π{sup −} p → π{sup +}π{sup −}π{sup −} p at 190 GeV/c. The results, presented in Section 1, show that a new state J{sup PC} = 1{sup ++} state never reported before, the a{sub 1}(1420), decaying to f{sub 0}(980)π followed by f{sub 0}(980) → ππ. In addition, the Collaboration reports an exotic J{sup PC} = 1{sup −+} state, the π{sub 1}(1600), which cannot be a quarkonium. Both states are likely to be a tetra-quark, i.e. qq{sup ¯}+qq{sup ¯} or a gluonic hybrid, a qq{sup ¯} object with an excited gluon inside it. Section 2 is devoted to a brief discussion of the central production of resonances, which is being investigated by both COMPASS and ALICE collaborations. However, the results are not yet released, so it is limited to a broad discussion of the central production, with emphasis on different analyses dictated by differences in the experimental setup.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Photoproduction of vector mesons in ultra-peripheral p–Pb and Pb–Pb collisions at the LHC with the ALICE experiment

Vector mesons are copiously produced in ultra-peripheral collisions. In these collisions, the impact parameter is larger than the sum of the radii of the two projectiles, implying that electromagnetic processes become dominant. The cross section of production of vector mesons is expected to be sensitive to the gluon distribution and can therefore probe nuclear gluon shadowing (Pb–Pb) and the gluon structure function in the nucleon (p-Pb). The ALICE Collaboration has performed the first measurements of the production of ρ{sup 0}, J/ψ and ψ/(2S) in Pb–Pb ultra-peripheral collision as well as the cross section for exclusive J/ψ photoproduction off protons in ultra-peripheral proton-lead collisions at the LHC. The results are compared to the STARLIGHT Monte Carlo and to QCD based models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

ALICE inner tracking system readout electronics prototype testing with the CERN "Giga Bit Transceiver''

The ALICE Collaboration is preparing a major detector upgrade for the LHC Run 3, which includes the construction of a new silicon pixel based Inner Tracking System (ITS). The ITS readout system consists of 192 readout boards to control the sensors and their power system, receive triggers, and deliver sensor data to the DAQ. To prototype various aspects of this readout system, an FPGA based carrier board and an associated FMC daughter card containing the CERN Gigabit Transceiver (GBT) chipset have been developed. Furthermore, this contribution describes laboratory and radiation testing results with this prototype board set.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Calibration of the photon spectrometer PHOS of the ALICE experiment

The procedure for the energy calibration of the high granularity electromagnetic calorimeter PHOS of the ALICE experiment is presented. The methods used to perform the relative gain calibration, to evaluate the geometrical alignment and the corresponding correction of the absolute energy scale, to obtain the nonlinearity correction coefficients and finally, to calculate the time-dependent calibration corrections, are discussed and illustrated by the PHOS performance in proton-proton (pp) collisions at √s = 13 TeV. After applying all corrections, the achieved mass resolutions for π 0 and η mesons for p T > 1.7 GeV/c are σ m π0 = 4.56 ± 0.03 MeV/c 2 and σ m η = 15.3 ± 1.0 MeV/c 2 , respectively.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Performance of the ALICE Electromagnetic Calorimeter

The performance of the electromagnetic calorimeter of the ALICE experiment during operation in 2010–2018 at the Large Hadron Collider is presented. After a short introduction into the design, readout, and trigger capabilities of the detector, the procedures for data taking, reconstruction, and validation are explained. The methods used for the calibration and various derived corrections are presented in detail. Subsequently, the capabilities of the calorimeter to reconstruct and measure photons, light mesons, electrons and jets are discussed. The performance of the calorimeter is illustrated mainly with data obtained with test beams at the Proton Synchrotron and Super Proton Synchrotron or in proton-proton collisions at $\sqrt{s}$ = 13 TeV, and compared to simulations.

47 OTHER INSTRUMENTATION↗