-
N. Abgrall,
A. Aduszkiewicz,
T. Anticic,
N. Antoniou,
J. Argyriades,
B. Baatar,
A. Blondel,
J. Blumer,
M. Bogomilov,
A. Bravar, [......],
M. Hartz,
A. K. Ichikawa,
H. Kubo,
A. D. Marino,
K. Matsuoka,
A. Murakami,
T. Nakaya,
K. Suzuki,
T. Yuan,
E. D. Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: The T2K long-baseline neutrino oscillation experiment in Japan needs precise
predictions of the initial neutrino flux. The highest precision can be reached
based on detailed measurements of hadron emission from the same target as used
by T2K exposed to a proton beam of the same kinetic energy of 30 GeV. The
corresponding data were recorded in 2007-2010 by the NA61/SHINE experiment at
the CERN SPS using a replica of the T2K graphite target. In this paper details
of the experiment, data taking, data analysis method and results from the 2007
pilot run are presented. Furthermore, the application of the NA61/SHINE
measurements to the predictions of the T2K initial neutrino flux is described
and discussed.
07/2012;
-
ALICE Collaboration,
B. Abelev,
J. Adam,
D. Adamova,
A. M. Adare,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
A. Agostinelli,
S. Aguilar Salazar, [......],
X. Zhang,
D. Zhou,
Y. Zhou,
F. Zhou,
X. Zhu,
A. Zichichi,
A. Zimmermann,
G. Zinovjev,
Y. Zoccarato,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The ALICE Collaboration has measured inclusive J/psi production in pp
collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results
presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and
have been obtained by measuring the electron and muon pair decay channels,
respectively. The integrated luminosities for the two channels are L^e_int=1.1
nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are
N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present
dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y
range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c.
The results are compared with previously published results at sqrt(s)=7 TeV and
with theoretical calculations.
03/2012;
-
K Aamodt,
B Abelev,
A Abrahantes Quintana,
D Adamova,
A M Adare,
M M Aggarwal,
Aglieri G Rinella,
A G Agocs,
A Agostinelli,
S Aguilar Salazar, [......],
D Zhou,
F Zhou,
Y Zhou,
X Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev,
ALICE Collaboration
Physics Letters B 01/2012; 708(3-5):249-264. · 3.95 Impact Factor
-
B Abelev,
A Abrahantes Quintana,
D Adamova,
A M Adare,
M M Aggarwal,
Aglieri G Rinella,
A G Agocs,
A Agostinelli,
S Aguilar Salazar,
Z Ahammed, [......],
D Zhou,
Y Zhou,
F Zhou,
X Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev,
ALICE Collaboration
Physics Letters B 01/2012; 710(4-5):557-568. · 3.95 Impact Factor
-
B Abelev,
J Adam,
D Adamova,
A M Adare,
M M Aggarwal,
Aglieri G Rinella,
A G Agocs,
A Agostinelli,
S Aguilar Salazar,
Z Ahammed, [......],
Y Zhou,
J Zhu,
X Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev,
M Zyzak,
ALICE Collaboration
Physics Letters B 01/2012; 717(1-3):151-161. · 3.95 Impact Factor
-
The Collaboration: N. Abgrall,
A. Aduszkiewicz,
T. Anticic,
N Antoniou,
J. Argyriades,
B Baatar,
A Blondel,
J. Blumer,
M. Bogusz,
L. Boldizsar, [......],
D. Veberic,
V. V. Vechernin,
G Vesztergombi,
A. Wilczek,
Z. Wlodarczyk,
A. Wojtaszek-Szwarc,
J. -G. Yi,
I. K. Yoo,
L. Zambelli,
W. Zipper
[show abstract]
[hide abstract]
ABSTRACT: Spectra of positively charged kaons in p+C interactions at 31 GeV/c were
measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is
based on the full set of data collected in 2007 with a graphite target with a
thickness of 4% of a nuclear interaction length. Interaction cross sections and
charged pion spectra were already measured using the same set of data. These
new measurements in combination with the published ones are required to improve
predictions of the neutrino flux for the T2K long baseline neutrino oscillation
experiment in Japan. In particular, the knowledge of kaon production is crucial
for precisely predicting the intrinsic electron neutrino component and the high
energy tail of the T2K beam. The results are presented as a function of
laboratory momentum in 2 intervals of the laboratory polar angle covering the
range from 20 up to 240 mrad. The kaon spectra are compared with predictions of
several hadron production models. Using the published pion results and the new
kaon data, the K+/\pi+ ratios are computed.
12/2011;
-
The ALICE Collaboration,
B. Abelev,
A. Abrahantes Quintana,
D. Adamova,
A. M. Adare,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
A. Agostinelli,
S. Aguilar Salazar, [......],
X Zhang,
F Zhou,
D Zhou,
Y Zhou,
X Zhu,
A. Zichichi,
A Zimmermann,
G. Zinovjev,
Y. Zoccarato,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The pt-differential inclusive production cross sections of the prompt charmed
mesons D0, D+, and D*+ in the rapidity range |y|<0.5 were measured in
proton-proton collisions at sqrt(s) = 7 TeV at the LHC using the ALICE
detector. Reconstructing the decays D0->K-pi+, D+->K-pi+pi+, D*+->D0pi+, and
their charge conjugates, about 8,400 D0, 2,900 D+, and 2,600 D*+ mesons with
1<pt<24 GeV/c were counted, after selection cuts, in a data sample of 3.14x10^8
events collected with a minimum-bias trigger (integrated luminosity L_int =
5/nb). The results are described within uncertainties by predictions based on
perturbative QCD.
11/2011;
-
The ALICE Collaboration,
B. Abelev,
A. Abrahantes Quintana,
D. Adamova,
A. M. Adare,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
A. Agostinelli,
S. Aguilar Salazar, [......],
X. Zhang,
F. Zhou,
D. Zhou,
Y. Zhou,
X. Zhu,
A. Zichichi,
A. Zimmermann,
G. Zinovjev,
Y. Zoccarato,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The ALICE Collaboration has studied J/psi production in pp collisions at
sqrt(s)=7 TeV at the LHC through its muon pair decay. The polar and azimuthal
angle distributions of the decay muons were measured, and results on the J/psi
polarization parameters lambda_theta and lambda_phi were obtained. The study
was performed in the kinematic region 2.5<y<4, 2<p_t<8 GeV/c, in the helicity
and Collins-Soper reference frames. In both frames, the polarization parameters
are compatible with zero, within uncertainties.
11/2011;
-
S. Gorbunov,
D. Rohr,
K. Aamodt,
T. Alt,
H. Appelshauser,
A. Arend,
M. Bach,
B. Becker,
S. Bottger,
T. Breitner, [......],
C. Stokkevag,
T.M. Steinbeck,
A. Szostak,
J. Thader,
T. Tveter,
K. Ullaland,
Z. Vilakazi,
R. Weis,
Zhongbao Yin,
P. Zelnicek
[show abstract]
[hide abstract]
ABSTRACT: The on-line event reconstruction in ALICE is performed by the High Level Trigger, which should process up to 2000 events per second in proton-proton collisions and up to 300 central events per second in heavy-ion collisions, corresponding to an input data stream of 30 GB/s. In order to fulfill the time requirements, a fast on-line tracker has been developed. The algorithm combines a Cellular Automaton method being used for a fast pattern recognition and the Kalman Filter method for fitting of found trajectories and for the final track selection. The tracker was adapted to run on Graphics Processing Units (GPU) using the NVIDIA Compute Unified Device Architecture (CUDA) framework. The implementation of the algorithm had to be adjusted at many points to allow for an efficient usage of the graphics cards. In particular, achieving a good overall workload for many processor cores, efficient transfer to and from the GPU, as well as optimized utilization of the different memories the GPU offers turned out to be critical. To cope with these problems a dynamic scheduler was introduced, which redistributes the workload among the processor cores. Additionally a pipeline was implemented so that the tracking on the GPU, the initialization and the output processed by the CPU, as well as the DMA transfer can overlap. The GPU tracking algorithm significantly outperforms the CPU version for large events while it entirely maintains its efficiency.
IEEE Transactions on Nuclear Science 09/2011; · 1.45 Impact Factor
-
M. Richter,
K. Aamodt,
T. Alt,
H. Appelshauser,
A. Arend,
B. Becker,
S. Bottger,
T. Breitner,
H. Busching,
C. Cicalo, [......], D. Rohrich,
B. Skaali,
T. Steinbeck,
A. Szostak,
J. Thader,
T.S. Tveter,
K. Ullaland,
Z. Vilakazi,
R. Weis,
P. Zelnicek
[show abstract]
[hide abstract]
ABSTRACT: The ALICE High Level Trigger comprises a large computing cluster, dedicated interfaces and software applications. It allows on-line event reconstruction of the full data stream of the ALICE experiment at up to 25 GByte/s. The commissioning campaign has passed an important phase since the startup of the Large Hadron Collider in November 2009. The system has been transferred into continuous operation with focus on the event reconstruction and first simple trigger applications. The paper reports for the first time on the achieved event reconstruction performance in the ALICE central barrel region.
IEEE Transactions on Nuclear Science 09/2011; · 1.45 Impact Factor
-
ALICE Collaboration,
K. Aamodt,
A. Abrahantes Quintana,
D. Adamova,
A. M. Adare,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
A. Agostinelli,
S. Aguilar Salazar, [......],
M. Zhalov,
X. Zhang,
D. Zhou,
F. Zhou,
Y. Zhou,
X. Zhu,
A. Zichichi,
G. Zinovjev,
Y. Zoccarato,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The ALICE experiment at the LHC has studied inclusive J/psi production at
central and forward rapidities in pp collisions at sqrt(s) = 7 TeV. In this
Letter, we report on the first results obtained detecting the J/psi through its
dilepton decay into e+e- and mu+mu- pairs in the rapidity range |y|<0.9 and
2.5<y<4, respectively, and with acceptance down to zero p_T. In the dielectron
channel the analysis was carried out on a data sample corresponding to an
integrated luminosity L_int = 5.6 nb^-1 and the number of signal events is
N_J/psi=352 \pm 32 (stat.) \pm 28 (syst.); the corresponding figures in the
dimuon channel are L_int = 15.6 nb ^-1 and N_J/\psi = 1924 \pm 77 (stat.) \pm
144(syst.). The measured production cross sections are sigma_J/psi (|y|<0.9) =
12.4 \pm 1.1 (stat.) \pm 1.8 (syst.) + 1.8 -2.7 (syst.pol.) \mub and
sigma_J/psi (2.5<y<4) = 6.31 \pm 0.25 (stat.) \pm 0.76 (syst.) +0.95 -1.96
(syst.pol.) \mub. The differential cross sections, in transverse momentum and
rapidity, of the J/psi were also measured.
05/2011;
-
N. Abgrall,
A. Aduszkiewicz,
B Andrieu,
T. Anticic,
N Antoniou,
J. Argyriades,
A. G. Asryan,
B Baatar,
A Blondel,
J. Blumer, [......],
M. Unger,
M Vassiliou,
V. V. Vechernin,
G Vesztergombi,
A. Wilczek,
Z. Wlodarczyk,
A Wojtaszek,
J. -G. Yi,
I. K. Yoo,
W. Zipper
[show abstract]
[hide abstract]
ABSTRACT: Interaction cross sections and charged pion spectra in p+C interactions at 31
GeV/c were measured with the large acceptance NA61/SHINE spectrometer at the
CERN SPS. These data are required to improve predictions of the neutrino flux
for the T2K long baseline neutrino oscillation experiment in Japan. A set of
data collected during the first NA61/SHINE run in 2007 with an isotropic
graphite target with a thickness of 4% of a nuclear interaction length was used
for the analysis. The measured p+C inelastic and production cross sections are
257.2 +- 1.9 +- 8.9 mb and 229.3 +- 1.9 +- 9.0 mb, respectively. Inclusive
production cross sections for negatively and positively charged pions are
presented as a function of laboratory momentum in 10 intervals of the
laboratory polar angle covering the range from 0 up to 420 mrad. The spectra
are compared with predictions of several hadron production models.
02/2011;
-
K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Abramyan,
D. Adamova,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
S. Aguilar Salazar, [......],
X Zhang,
D Zhou,
S Zhou,
J Zhu,
A. Zichichi,
A Zinchenko,
G. Zinovjev,
Y. Zoccarato,
V. Zychacek,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: We report on the measurement of two-pion correlation functions from pp
collisions at sqrt(s)=900 GeV performed by the ALICE experiment at the Large
Hadron Collider. Our analysis shows an increase of the HBT radius with
increasing event multiplicity, in line with other measurements done in
particle- and nuclear collisions. Conversely, the strong decrease of the radius
with increasing transverse momentum, as observed at RHIC and at Tevatron, is
not manifest in our data.
07/2010;
-
Authors: ALICE Collaboration: K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Abramyan,
D. Adamova,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
S. Aguilar Salazar, [......],
X Zhang,
D Zhou,
S Zhou,
J Zhu,
A. Zichichi,
A Zinchenko,
G. Zinovjev,
Y. Zoccarato,
V. Zychacek,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at $\sqrt{s} = 0.9$ and $7$~TeV during the initial running periods of the Large Hadron Collider(LHC). The measurement covers the transverse momentum interval $0.45 < p_{\rm{t}} < 1.05$~GeV/$c$ and rapidity $|y| < 0.5$. The ratio is measured to be $R_{|y| < 0.5} = 0.957 \pm 0.006 (stat.) \pm 0.014 (syst.)$ at $0.9$~TeV and $R_{|y| < 0.5} = 0.991 \pm 0.005 (stat.) \pm 0.014 (syst.)$ at $7$~TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions. Comment: Submitted in PRL: 12 pages, 4 figures
06/2010;
-
M. Richter,
K. Aamodt,
T. Alt,
H. Appelshäuser,
A. Arend,
B. Becker,
S. Böttger,
T. Breitner,
H. Büsching,
C. Cicalo, [......], D. Rohrich,
B. Skaali,
T. Steinbeck,
A. Szostak,
J. Thäder,
T.S. Tveter,
K. Ullaland,
Z. Vilakazi,
R. Weis,
P. Zelnicek
[show abstract]
[hide abstract]
ABSTRACT: The ALICE High Level Trigger comprises a large computing cluster, dedicated interfaces and software applications. It allows on-line event reconstruction of the full data stream of the ALICE experiment at up to 25 GByte/s. The commissioning campaign has passed an important phase since the startup of the Large Hadron Collider in Nov 2009. The system has been transferred into continuous operation with focus on the event reconstruction and first simple trigger applications. The paper reports for the first time on the achieved event reconstruction performance in the ALICE central barrel region.
Real Time Conference (RT), 2010 17th IEEE-NPSS; 06/2010
-
S. Gorbunov,
K. Aamodt,
T. Alt,
H. Appelshauser,
A. Arend,
B. Becker,
S. Bottger,
T. Breitner,
H. Busching,
S. Chattopadhyay, [......], D. Rohrich,
B. Skaali,
T. Steinbeck,
A. Szostak,
J. Thader,
T. Tveter,
K. Ullaland,
Z. Vilakazi,
R. Weis,
P. Zelnicek
[show abstract]
[hide abstract]
ABSTRACT: The on-line event reconstruction in ALICE is performed by the High Level Trigger, which should process up to 2000 events per second in proton-proton collisions and up to 200 central events per second in heavy-ion collisions, corresponding to an input data stream of 30 GB/s. In order to fulfil the time requirements, a fast on-line tracker has been developed which can optionally use GPU hardware accelerators. The algorithm combines a Cellular Automaton method being used for a fast pattern recognition and the Kalman Filter method for fit of found trajectories and for the final track selection. A fast estimate of the vertex position is based on measurements from the Silicon Pixel Detector. The vertexer is used for the on line monitoring of the ALICE interaction point.
Real Time Conference (RT), 2010 17th IEEE-NPSS; 06/2010
-
K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Abramyan,
D. Adamova,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
S. Aguilar Salazar, [......],
X Zhang,
D Zhou,
S Zhou,
J Zhu,
A. Zichichi,
A Zinchenko,
G. Zinovjev,
Y. Zoccarato,
V. Zychacek,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy sqrt(s) = 7 TeV, were measured in the central pseudorapidity region |eta| < 1. Comparisons are made with previous measurements at sqrt(s) = 0.9 TeV and 2.36 TeV. At sqrt(s) = 7 TeV, for events with at least one charged particle in |eta| < 1, we obtain dNch/deta = 6.01 +- 0.01 (stat.) +0.20 -0.12 (syst.). This corresponds to an increase of 57.6% +- 0.4% (stat.) +3.6 -1.8% (syst.) relative to collisions at 0.9 TeV, significantly higher than calculations from commonly used models. The multiplicity distribution at 7 TeV is described fairly well by the negative binomial distribution. Comment: accepted by EPJC - version2: small updates to the text and author list
04/2010;
-
K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Abramyan,
D. Adamova,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
S. Aguilar Salazar, [......],
X Zhang,
D Zhou,
S Zhou,
J Zhu,
A. Zichichi,
A Zinchenko,
G. Zinovjev,
Y. Zoccarato,
V. Zychacek,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range |eta| < 1.4. In the central region (|eta| < 0.5), at 0.9 TeV, we measure charged-particle pseudorapidity density dNch/deta = 3.02 +- 0.01 (stat.) +0.08 -0.05 (syst.) for inelastic interactions, and dNch/deta = 3.58 +- 0.01 (stat.) +0.12 -0.12 (syst.) for non-single-diffractive interactions. At 2.36 TeV, we find dNch/deta = 3.77 +- 0.01 (stat.) +0.25 -0.12 (syst.) for inelastic, and dNch/deta = 4.43 +- 0.01 (stat.) +0.17 -0.12 (syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7% +- 0.5% (stat.) +5.7% -2.8% (syst.) for inelastic and 23.7% +- 0.5% (stat.) +4.6% -1.1% (syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton-antiproton data and to model predictions. Comment: accepted by EPJC; version2: minor updates to the text and author list
04/2010;
-
J. Alme,
Y. Andres,
H. Appelshauser,
S. Bablok,
N. Bialas,
R. Bolgen,
U. Bonnes,
R Bramm,
P. Braun-Munzinger,
R. Campagnolo, [......],
E Stenlund,
R. Stock,
P. Strmen,
I. Szarka,
K. Ullaland,
D Vranic,
R Veenhof,
J. Westergaard,
J. Wiechula,
B. Windelband
[show abstract]
[hide abstract]
ABSTRACT: The design, construction, and commissioning of the ALICE Time-Projection Chamber (TPC) is described. It is the main device for pattern recognition, tracking, and identification of charged particles in the ALICE experiment at the CERN LHC. The TPC is cylindrical in shape with a volume close to 90 m^3 and is operated in a 0.5 T solenoidal magnetic field parallel to its axis. In this paper we describe in detail the design considerations for this detector for operation in the extreme multiplicity environment of central Pb--Pb collisions at LHC energy. The implementation of the resulting requirements into hardware (field cage, read-out chambers, electronics), infrastructure (gas and cooling system, laser-calibration system), and software led to many technical innovations which are described along with a presentation of all the major components of the detector, as currently realized. We also report on the performance achieved after completion of the first round of stand-alone calibration runs and demonstrate results close to those specified in the TPC Technical Design Report. Comment: 55 pages, 82 figures
01/2010;
-
The ALICE Collaboration,
K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Acero,
D. Adamova,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs, [......],
X Zhang,
D Zhou,
S Zhou,
J Zhu,
A. Zichichi,
A Zinchenko,
G. Zinovjev,
M. Zinovjev,
Y. Zoccarato,
V. Zychacek
[show abstract]
[hide abstract]
ABSTRACT: On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |eta| < 0.5, we obtain dNch/deta = 3.10 +- 0.13 (stat.) +- 0.22 (syst.) for all inelastic interactions, and dNch/deta = 3.51 +- 0.15 (stat.) +- 0.25 (syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton--antiproton interactions at the same centre-of-mass energy at the CERN SppS collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase. Comment: First ALICE physics publication v2: Small corrections to the text, author list and references
11/2009;
