-
B Abelev,
J Adam,
D Adamová,
A M Adare,
M M Aggarwal,
G Aglieri Rinella,
M Agnello,
A G Agocs,
A Agostinelli,
Z Ahammed, [......],
D Zhou,
X Zhu,
J Zhu,
H Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev,
M Zyzak
[show abstract]
[hide abstract]
ABSTRACT: The transverse momentum (p_{T}) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p+Pb collisions at sqrt[s_{NN}]=5.02 TeV with the ALICE detector at the LHC. The p_{T} spectra measured near central rapidity in the range 0.5<p_{T}<20 GeV/c exhibit a weak pseudorapidity dependence. The nuclear modification factor R_{pPb} is consistent with unity for p_{T} above 2 GeV/c. This measurement indicates that the strong suppression of hadron production at high p_{T} observed in Pb+Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.
Physical Review Letters 02/2013; 110(8):082302. · 7.37 Impact Factor
-
B Abelev,
J Adam,
D Adamová,
A M Adare,
M M Aggarwal,
G Aglieri Rinella,
M Agnello,
A G Agocs,
A Agostinelli,
Z Ahammed, [......],
Y Zhou,
J Zhu,
H Zhu,
X Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev,
M Zyzak
[show abstract]
[hide abstract]
ABSTRACT: The charged-particle pseudorapidity density measured over four units of pseudorapidity in nonsingle-diffractive p+Pb collisions at a center-of-mass energy per nucleon pair sqrt[s_{NN}]=5.02 TeV is presented. The average value at midrapidity is measured to be 16.81±0.71 (syst), which corresponds to 2.14±0.17 (syst) per participating nucleon, calculated with the Glauber model. This is 16% lower than in nonsingle-diffractive pp collisions interpolated to the same collision energy and 84% higher than in d+Au collisions at sqrt[s_{NN}]=0.2 TeV. The measured pseudorapidity density in p+Pb collisions is compared to model predictions and provides new constraints on the description of particle production in high-energy nuclear collisions.
Physical Review Letters 01/2013; 110(3):032301. · 7.37 Impact Factor
-
B Abelev,
J Adam,
D Adamová,
A M Adare,
M M Aggarwal,
G Aglieri Rinella,
A G Agocs,
A Agostinelli,
S Aguilar Salazar,
Z Ahammed, [......],
D Zhou,
F Zhou,
J Zhu,
X Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev,
M Zyzak
[show abstract]
[hide abstract]
ABSTRACT: Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudorapidity range |η|<0.8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal correlations observed at RHIC and LHC energies.
Physical Review Letters 01/2013; 110(1):012301. · 7.37 Impact Factor
-
B Abelev,
J Adam,
D Adamová,
A M Adare,
M M Aggarwal,
G Aglieri Rinella,
A G Agocs,
A Agostinelli,
S Aguilar Salazar,
Z Ahammed, [......],
D Zhou,
F Zhou,
Y Zhou,
J Zhu,
X Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The first measurement of neutron emission in electromagnetic dissociation of ^{208}Pb nuclei at the LHC is presented. The measurement is performed using the neutron zero degree calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at sqrt[s_{NN}]=2.76 TeV with neutron emission are σ_{singleEMD}=187.4±0.2(stat)_{-11.2}^{+13.2}(syst) b and σ_{mutualEMD}=5.7±0.1(stat)±0.4(syst) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.
Physical Review Letters 12/2012; 109(25):252302. · 7.37 Impact Factor
-
B Abelev,
J Adam,
D Adamová,
A M Adare,
M M Aggarwal,
G Aglieri Rinella,
A G Agocs,
A Agostinelli,
S Aguilar Salazar,
Z Ahammed, [......],
Y Zhou,
F Zhou,
J Zhu,
X Zhu,
A Zichichi,
A Zimmermann,
G Zinovjev,
Y Zoccarato,
M Zynovyev,
M Zyzak
[show abstract]
[hide abstract]
ABSTRACT: In this Letter we report the first results on π^{±}, K^{±}, p, and p[over ¯] production at midrapidity (|y|<0.5) in central Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV, measured by the ALICE experiment at the LHC. The p_{T} distributions and yields are compared to previous results at sqrt[s_{NN}]=200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with sqrt[s_{NN}], which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.
Physical Review Letters 12/2012; 109(25):252301. · 7.37 Impact Factor
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
H. Al-Bataineh,
H. Al-Ta'ani,
J. Alexander,
A. Angerami, [......],
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
A. Zelenski,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: The jet fragmentation function is measured with direct photon-hadron
correlations in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. The p_T of the
photon is an excellent approximation to the initial p_T of the jet and the
ratio z_T=p_T^h/p_T^\gamma is used as a proxy for the jet fragmentation
function. A statistical subtraction is used to extract the direct photon-hadron
yields in Au+Au collisions while a photon isolation cut is applied in p+p. I_
AA, the ratio of jet fragment yield in Au+Au to that in p+p, indicates
modification of the jet fragmentation function. Suppression, most likely due to
energy loss in the medium, is seen at high z_T. The fragment yield at low z_T
is enhanced at large angles. Such a trend is expected from redistribution of
the lost energy into increased production of low-momentum particles.
12/2012;
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
H. Al-Bataineh,
H. Al-Ta'ani,
J. Alexander,
K. R. Andrews, [......],
Z. You,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
A. Zelenski,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: The three Upsilon states, Upsilon(1S+2S+3S), are measured in d+Au and p+p
collisions at sqrt(s_NN)=200 GeV and rapidities 1.2<|y|<2.2 by the PHENIX
experiment at the Relativistic Heavy-Ion Collider. Cross sections for the
inclusive Upsilon(1S+2S+3S) production are obtained. The inclusive yields per
binary collision for d+Au collisions relative to those in p+p collisions
(R_dAu) are found to be 0.62 +/- 0.26 (stat) +/- 0.13 (syst) in the gold-going
direction and 0.91 +/- 0.33 (stat) +/- 0.16 (syst) in the deuteron-going
direction. The measured results are compared to a nuclear-shadowing model,
EPS09 [JHEP 04, 065 (2009)], combined with a final-state breakup cross section,
sigma_br, and compared to lower energy p+A results. We also compare the results
to the PHENIX J/psi results [Phys. Rev. Lett. 107, 142301 (2011)]. The rapidity
dependence of the observed Upsilon suppression is consistent with lower energy
p+A measurements.
11/2012;
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
H. Al-Ta'ani,
A. Angerami,
K. Aoki, [......],
S. Yokkaichi,
G. R. Young,
I. Younus,
Z. You,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: We previously reported [Phys. Rev. D 82, 112008 (2010)] measurements of
transverse single-spin asymmetries, A_N, in J/psi production from transversely
polarized p+p collisions at sqrt(s)=200 GeV with data taken by the PHENIX
experiment at the Relativistic Heavy Ion Collider in 2006 and 2008.
Subsequently, we have found errors in the analysis procedures for the 2008
data, which resulted in an erroneous value for the extracted A_N. The errors
affected the sorting of events into the correct left/right and forward/backward
bins. This produced an incorrect value for the 2008 result, but the 2006 result
is unaffected. We have conducted two independent reanalyses with these errors
corrected, and we present here the corrected values for the 2008 data and the
combined results for 2006 and 2008. The new combined spin asymmetry in the
forward region is A_N = -0.026+/-0.026(stat)+/-0.003(sys). Since this asymmetry
is consistent with zero, we no longer claim that our results suggest a possible
non-zero trigluon correlation function in transversely polarized protons.
10/2012;
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
K. Aoki,
L. Aphecetche,
J. Asai, [......],
J. Ying,
S. Yokkaichi,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: The energy dependence of the single-transverse-spin asymmetry, A_N, and the
cross section for neutron production at very forward angles were measured in
the PHENIX experiment at RHIC for polarized p+p collisions at sqrt(s)=200 GeV.
The neutrons were observed in forward detectors covering an angular range of up
to 2.2 mrad. We report results for neutrons with momentum fraction of x_F=0.45
to 1.0. The energy dependence of the measured cross sections were consistent
with x_F scaling, compared to measurements by an ISR experiment which measured
neutron production in unpolarized p+p collisions at sqrt(s)=30.6--62.7 GeV. The
cross sections for large x_F neutron production for p+p collisions, as well as
those in e+p collisions measured at HERA, are described by a pion exchange
mechanism. The observed forward neutron asymmetries were large, reaching
A_N=-0.08+/-0.02 for x_F=0.8; the measured backward asymmetries, for negative
x_F, were consistent with zero. The observed asymmetry for forward neutron
production is discussed within the pion exchange framework, with interference
between the spin-flip amplitude due to the pion exchange and nonflip amplitudes
from all Reggeon exchanges. Within the pion exchange description, the measured
neutron asymmetry is sensitive to the contribution of other Reggeon exchanges
even for small amplitudes.
09/2012;
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
K. Aoki,
L. Aphecetche,
R. Armendariz, [......],
S. Yokkaichi,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
J. Zimanyi,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: Heavy-flavor production in p + p collisions is a good test of perturbative-quantumchromodynamics
(pQCD) calculations. Modification of heavy-flavor production in heavy-ion collisions relative
to binary-collision scaling from p + p results, quantified with the nuclear-modification factor (RAA), provides
information on both cold- and hot-nuclear-matter effects. Midrapidity heavy-flavor RAA measurements at the Relativistic Heavy Ion Collider have challenged parton-energy-loss models and resulted in upper limits on the viscosity-entropy ratio that are near the quantum lower bound. Such measurements have not been made in the forward-rapidity region. The charm-production cross section in p + p collisions at √s = 200 GeV, integrated over pT and in the rapidity range 1.4 < y < 1.9, is found to be dσc ¯ c/dy = 0.139 ± 0.029 (stat) +0.051 −0.058 (syst) mb. This result is consistent with a perturbative fixed-order-plus-next-to-leading-log calculation within scale uncertainties and is also consistent with expectations based on the corresponding midrapidity charm-production cross section measured by PHENIX. The RAA for heavy-flavor muons in Cu + Cu collisions is measured in three centrality bins for 1 < pT < 4 GeV/c. Suppression relative to binary-collision scaling (RAA < 1) increases with centrality. Within experimental and theoretical uncertainties, the measured charm yield in p + p collisions is consistent with state-of-the-art pQCD calculations. Suppression in central Cu + Cu collisions suggests the presence of significant cold-nuclear-matter effects and final-state energy loss.
Physical Review C 08/2012; 86:024909. · 3.31 Impact Factor
-
A. Adare,
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
A. Al-Jamel,
J. Alexander,
A. Angerami, [......],
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: Direct photons have been measured in sqrt(s_NN)=200 GeV d+Au collisions at
midrapidity. A wide p_T range is covered by measurements of nearly-real virtual
photons (1<p_T<6 GeV/c) and real photons (5<p_T<16 GeV/c). The invariant yield
of the direct photons in d+Au collisions over the scaled p+p cross section is
consistent with unity. Theoretical calculations assuming standard cold nuclear
matter effects describe the data well for the entire p_T range. This indicates
that the large enhancement of direct photons observed in Au+Au collisions for
1.0<p_T<2.5 GeV/c is due to a source other than the initial-state nuclear
effects.
08/2012;
-
A. Adare,
S. Afanasiev,
C. Aidala,
N.N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
K. Aoki,
L. Aphecetche,
J. Asai, [......],
J. Ying,
S. Yokkaichi,
G.R. Young,
I. Younus,
I.E. Yushmanov,
W.A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: The differential cross section for the production of direct photons in p+p collisions at √s = 200
GeV at midrapidity was measured in the PHENIX detector at the Relativistic Heavy Ion Collider.
Inclusive-direct photons were measured in the transverse momentum range from 5.5–25 GeV/c,
extending the range beyond previous measurements. Event structure was studied with an isolation
criterion. Next-to-leading-order perturbative-quantum-chromodynamics calculations give a good
description of the spectrum. When the cross section is expressed versus xT , the PHENIX data
are seen to be in agreement with measurements from other experiments at different center-of-mass
energies.
Physical Review C 06/2012; · 3.31 Impact Factor
-
ALICE Collaboration,
B. Abelev,
J. Adam,
D. Adamová,
A. M. Adare,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
A. Agostinelli,
S. Aguilar Salazar, [......],
X. Zhang,
Y. Zhou,
D. Zhou,
F. Zhou,
X. Zhu,
A. Zichichi,
A. Zimmermann,
G. Zinovjev,
Y. Zoccarato,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The ALICE Collaboration reports the measurement of the relative J/ψ
yield as a function of charged particle pseudorapidity density
dNch/dη in pp collisions at s=7 TeV at the LHC.
J/ψ particles are detected for pt>0, in the rapidity
interval |y|<0.9 via decay into e+e-, and
in the interval 2.5<y<4.0 via decay into
μ+μ- pairs. An approximately linear
increase of the J/ψ yields normalized to their event average
(dN/dy)/<dN/dy> with
(dNch/dη)/<dNch/dη> is observed in
both rapidity ranges, where dNch/dη is measured within
|η|<1 and pt>0. In the highest multiplicity
interval with <dNch/dη(bin)>=24.1, corresponding to
four times the minimum bias multiplicity density, an enhancement
relative to the minimum bias J/ψ yield by a factor of about 5 at
2.5<y<4 (8 at |y|<0.9) is observed.
Physics Letters B 05/2012; 712:165-175. · 3.95 Impact Factor
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
K. Aoki,
L. Aphecetche,
J. Asai, [......],
J. Ying,
S. Yokkaichi,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: The differential cross section for the production of direct photons in p+p
collisions at sqrt(s)=200 GeV at midrapidity was measured in the PHENIX
detector at the Relativistic Heavy Ion Collider. Inclusive-direct photons were
measured in the transverse-momentum range from 5.5--25 GeV/c, extending the
range beyond previous measurements. Event structure was studied with an
isolation criterion. Next-to-leading-order perturbative-quantum-chromodynamics
calculations give a good description of the spectrum. When the cross section is
expressed versus x_T, the PHENIX data are seen to be in agreement with
measurements from other experiments at different center-of-mass energies.
05/2012;
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
A. Angerami,
K. Aoki,
N. Apadula, [......],
S. Yokkaichi,
Z. You,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: We report on charmonium measurements [J/ψ (1S), ψ′ (2S), and χc (1P)] in p+p collisions at √s=200 GeV. We find that the fraction of J/ψ coming from the feed-down decay of ψ′ and χc in the midrapidity region (|y|<0.35) is 9.6±2.4% and 32±9%, respectively. We also present the pT and rapidity dependencies of the J/ψ yield measured via dielectron decay at midrapidity (|y|<0.35) and via dimuon decay at forward rapidity (1.2<|y|<2.2). The statistical precision greatly exceeds that reported in our previous publication [ Phys. Rev. Lett. 98 232002 (2007)]. The new results are compared with other experiments and discussed in the context of current charmonium production models.
Phys. Rev. D. 05/2012; 85(9).
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
A. Angerami,
K. Aoki,
N. Apadula, [......],
S. Yokkaichi,
Z. You,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: We report on charmonium measurements [J/ψ (1S), ψ′ (2S), and χc (1P)] in p+p collisions at √s=200 GeV. We find that the fraction of J/ψ coming from the feed-down decay of ψ′ and χc in the midrapidity region (|y|<0.35) is 9.6±2.4% and 32±9%, respectively. We also present the pT and rapidity dependencies of the J/ψ yield measured via dielectron decay at midrapidity (|y|<0.35) and via dimuon decay at forward rapidity (1.2<|y|<2.2). The statistical precision greatly exceeds that reported in our previous publication [ Phys. Rev. Lett. 98 232002 (2007)]. The new results are compared with other experiments and discussed in the context of current charmonium production models.
Physical Review D 05/2012; 85:092004. · 4.56 Impact Factor
-
The ALICE Collaboration,
K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Acero,
D. Adamová,
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. Zycháček
[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 450GeV 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 |η|<0.5, we obtain dN
ch/dη=3.10±0.13(stat.)±0.22(syst.) for all inelastic interactions, and dN
ch/dη=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 Sp
[`(p)]\overline{\mathrm{p}}
S 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.
European Physical Journal C 04/2012; 65(1):111-125. · 3.63 Impact Factor
-
The ALICE Collaboration,
K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Abramyan,
D. Adamová,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs, [......],
X. Zhang,
D. Zhou,
S. Zhou,
J. Zhu,
A. Zichichi,
A. Zinchenko,
G. Zinovjev,
Y. Zoccarato,
V. Zycháček,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The production of π
+, π
−, K+, K−, p, and [`(p)]\overline{\mathrm{p}} at mid-rapidity has been measured in proton-proton collisions at Ös = 900GeV\sqrt{s} = 900~\mathrm{GeV} with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon
detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta.
Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon
transverse momentum (p
t) spectra. Since these various particle identification tools give the best separation capabilities over different momentum
ranges, the results are combined to extract spectra from p
t=100MeV/c to 2.5 GeV/c. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and
the mean p
t are compared with previous measurements, and the trends as a function of collision energy are discussed.
European Physical Journal C 04/2012; 71(6):1-22. · 3.63 Impact Factor
-
K. Aamodt,
A. Abrahantes Quintana,
D. Adamová,
A. M. Adare,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs,
S. Aguilar Salazar,
Z. Ahammed,
N. Ahmad, [......],
P. Zelnicek,
A. Zenin,
I. Zgura,
M. Zhalov,
X. Zhang,
D. Zhou,
A. Zichichi,
G. Zinovjev,
Y. Zoccarato,
M. Zynovyev
[show abstract]
[hide abstract]
ABSTRACT: The production of mesons containing strange quarks ($\mbox {$\mbox {, φ) and both singly and doubly strange baryons ($\mbox {$\mbox {, $\mbox {$\mbox {, and $\mbox {$\mbox {) are measured at mid-rapidity in pp collisions at
_boxclose_boxclose_boxclose\sqrt{s}=0.9TeV{\rm TeV} with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250k minimum bias events recorded
in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at mid-rapidity for inelastic pp collisions are presented. For mesons, we report yields
(〈dN/dy〉) of 0.184±0.002(stat.)±0.006(syst.) for $\mbox {$\mbox { and 0.021±0.004(stat.)±0.003(syst.) forφ. For baryons, we find 〈dN/dy〉=0.048±0.001(stat.)±0.004(syst.) for $\mbox {$\mbox {, 0.047±0.002(stat.)±0.005(syst.) for $\mbox {$\mbox { and 0.0101±0.0020(stat.)±0.0009(syst.) for $\mbox {$\mbox {. The results are also compared with predictions for identified particle spectra from QCD-inspired models and provide a baseline
for comparisons with both future pp measurements at higher energies and heavy-ion collisions.
European Physical Journal C 04/2012; 71(3):1-24. · 3.63 Impact Factor
-
The ALICE Collaboration,
K. Aamodt,
N. Abel,
U. Abeysekara,
A. Abrahantes Quintana,
A. Abramyan,
D. Adamová,
M. M. Aggarwal,
G. Aglieri Rinella,
A. G. Agocs, [......],
X. Zhang,
D. Zhou,
S. Zhou,
J. Zhu,
A. Zichichi,
A. Zinchenko,
G. Zinovjev,
Y. Zoccarato,
V. Zycháček,
M. Zynovyev
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ABSTRACT: Charged-particle production was studied in proton–proton collisions collected at the LHC with the ALICE detector at centre-of-mass
energies 0.9TeV and 2.36TeV in the pseudorapidity range |η|<1.4. In the central region (|η|<0.5), at 0.9TeV, we measure charged-particle pseudorapidity density dNch/dh = 3.02±0.01(stat.)+0.08-0.05(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.02\pm 0.01(\mathit{stat.})^{+0.08}_{-0.05}(\mathit{syst.}) for inelastic interactions, and dNch/dh = 3.58±0.01(stat.)+0.12-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.58\pm0.01(\mathit{stat.})^{+0.12}_{-0.12}(\mathit{syst.}) for non-single-diffractive interactions. At 2.36TeV, we find dNch/dh = 3.77±0.01(stat.)+0.25-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.77\pm0.01(\mathit{stat.})^{+0.25}_{-0.12}(\mathit{syst.}) for inelastic, and dNch/dh = 4.43±0.01(stat.)+0.17-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=4.43\pm0.01(\mathit{stat.})^{+0.17}_{-0.12}(\mathit{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.)24.7\%\pm0.5\%(\mathit{stat.})^{+5.7}_{-2.8}\%(\mathit{syst.}) for inelastic and 23.7%±0.5%(stat.)+4.6-1.1%(syst.)23.7\%\pm0.5\%(\mathit{stat.})^{+4.6}_{-1.1}\%(\mathit{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.
European Physical Journal C 04/2012; 68(1):89-108. · 3.63 Impact Factor
