| 1. |
- Abelev, Betty, et al.
(författare)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Abelev, Betty, et al.
(författare)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :11
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 4. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 5. |
- Das, Sanjeev, et al.
(författare)
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Effect of static and dynamic ageing on friction and wear behaviour of aluminium 6082 alloy
- 2012
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Ingår i: 15th Nordic Symposium on Tribology - NordTrib 2012. - Trondheim : Department of Geography, Norwegian University of Science and Technology.
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Konferensbidrag (refereegranskat)abstract
- In recent past, warm forming processes have been used successfully to increase the strength of age-hardenable alloys by dynamic precipitation. However, the influence of dynamic age hardening on the wear and friction behaviour of age-hardenable aluminium alloy is not clear. Therefore, in the present investigation the effect of static and dynamic ageing on the friction and wear behaviour of aluminium 6082 alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The aluminium samples used in the present study were in as-cast, solitionised and peak aged conditions. Optical microscope revealed the presence of dendritic structure in both as-cast and solitionised samples. Scanning electron microscope analysis of the debris and worn surfaces revealed the wear mechanism and role of precipitates on the friction and wear results. At low temperature (40 C), the frictional behaviour of as-cast, solitionised and peak aged samples were similar. The wear rates at 40 C increased with increase in the amount of strain inside the specimens due to fine precipitations. At 180 C, a significant variation in the frictional behaviour of different specimens was observed. The wear rate of solitionised specimens at 180 C is higher compared to as-cast and aged specimens. The absence of hard phases at initial stage of the test and subsequent dynamic precipitates restricted to a thin layer were responsible for the increase in wear rate.
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| 6. |
- Das, Sanjeev, et al.
(författare)
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Effect of static and dynamic ageing on wear and friction behavior of aluminum 6082 alloy
- 2013
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 60, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation the effect of static and dynamic ageing on the wear and friction behavior of aluminum alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The AA 6082 alloy samples used in the present study were in as-cast, solutionized and peak aged conditions. Scanning electron microscope analysis of the debris and worn surfaces revealed the role of precipitates on the dry sliding wear behavior. Frictional behavior varies significantly for all the conditions at elevated temperature (180 °C) compared to room temperature (40 °C). Such response was attributed to the dynamic precipitations during elevated temperature test.
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