We present a new analysis framework called “Correlation Analysis Tool using the Schrödinger equation” (CATS) which computes the two-particle femtoscopy correlation function
C
(
k
), with
k
being the ...relative momentum for the particle pair. Any local interaction potential and emission source function can be used as an input and the wave function is evaluated exactly. In this paper we present a study on the sensitivity of
C
(
k
) to the interaction potential for different particle pairs: p–p, p–
Λ
,
K
-
–p,
K
+
–p, p–
Ξ
-
and
Λ
–
Λ
. For the p–p Argonne
v
18
and Reid Soft-Core potentials have been tested. For the other pair systems we present results based on strong potentials obtained from effective Lagrangians such as
χ
EFT for p–
Λ
, Jülich models for
K
(
K
¯
)
–N and Nijmegen models for
Λ
–
Λ
. For the p–
Ξ
-
pairs we employ the latest lattice results from the HAL QCD collaboration. Our detailed study of different interacting particle pairs as a function of the source size and different potentials shows that femtoscopic measurements can be exploited in order to constrain the final state interactions among hadrons. In particular, small collision systems of the order of 1 fm, as produced in pp collisions at the LHC, seem to provide a suitable environment for quantitative studies of this kind.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This work provides the first combined analysis of low-energy pΛ scattering, considering both cross section and correlation data. The obtained results establish the most stringent constraints to date ...on the two-body pΛ interaction, pointing to a weaker attraction than so far accepted. The best set of scattering lengths for the spin singlet and triplet are found to range from f0,f1=(2.1,1.56) to (3.34,1.18) fm. With a chiral NY potential fine-tuned to those scattering parameters, the in-medium properties of the Λ are explored and a potential depth of UΛ=−36.3±1.3(stat)−6.2+2.5(syst) MeV is found at nuclear matter saturation density.
A
bstract
The inclusive J
/ψ
production in Pb–Pb collisions at the center-of-mass energy per nucleon pair
s
NN
= 5
.
02 TeV, measured with the ALICE detector at the CERN LHC, is reported. The J
/ψ
...meson is reconstructed via the dimuon decay channel at forward rapidity (2
.
5
< y <
4) down to zero transverse momentum. The suppression of the J
/ψ
yield in Pb–Pb collisions with respect to binary-scaled pp collisions is quantified by the nuclear modification factor (
R
AA
). The
R
AA
at
s
NN
= 5
.
02 TeV is presented and compared with previous measurements at
s
NN
= 2
.
76 TeV as a function of the centrality of the collision, and of the J
/ψ
transverse momentum and rapidity. The inclusive J
/ψ R
AA shows a suppression increasing toward higher transverse momentum, with a steeper dependence for central collisions. The modification of the J
/ψ
average transverse momentum and average squared transverse momentum is also studied. Comparisons with the results of models based on a transport equation and on statistical hadronization are carried out.
We present results on transverse momentum (
p
T
) and rapidity (
y
) differential production cross sections, mean transverse momentum and mean transverse momentum square of inclusive
J
/
ψ
and
ψ
(
2
...S
)
at forward rapidity (
2.5
<
y
<
4
) as well as
ψ
(
2
S
)
-to-
J
/
ψ
cross section ratios. These quantities are measured in pp collisions at center of mass energies
s
=
5.02
and 13 TeV with the ALICE detector. Both charmonium states are reconstructed in the dimuon decay channel, using the muon spectrometer. A comprehensive comparison to inclusive charmonium cross sections measured at
s
=
2.76
, 7 and 8 TeV is performed. A comparison to non-relativistic quantum chromodynamics and fixed-order next-to-leading logarithm calculations, which describe prompt and non-prompt charmonium production respectively, is also presented. A good description of the data is obtained over the full
p
T
range, provided that both contributions are summed. In particular, it is found that for
p
T
>
15
GeV/
c
the non-prompt contribution reaches up to 50% of the total charmonium yield.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Charged-particle spectra at midrapidity are measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair sNN=5.02 TeV and presented in centrality classes ranging from most ...central (0–5%) to most peripheral (95–100%) collisions. Possible medium effects are quantified using the nuclear modification factor (RAA) by comparing the measured spectra with those from proton–proton collisions, scaled by the number of independent nucleon–nucleon collisions obtained from a Glauber model. At large transverse momenta (8<pT<20GeV/c), the average RAA is found to increase from about 0.15 in 0–5% central to a maximum value of about 0.8 in 75–85% peripheral collisions, beyond which it falls off strongly to below 0.2 for the most peripheral collisions. Furthermore, RAA initially exhibits a positive slope as a function of pT in the 8–20 GeV/c interval, while for collisions beyond the 80% class the slope is negative. To reduce uncertainties related to event selection and normalization, we also provide the ratio of RAA in adjacent centrality intervals. Our results in peripheral collisions are consistent with a PYTHIA-based model without nuclear modification, demonstrating that biases caused by the event selection and collision geometry can lead to the apparent suppression in peripheral collisions. This explains the unintuitive observation that RAA is below unity in peripheral Pb–Pb, but equal to unity in minimum-bias p–Pb collisions despite similar charged-particle multiplicities.
The first evidence of spin alignment of vector mesons ( K*0 and ϕ ) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element ρ 00 is measured at ...midrapidity ( | y | < 0.5 ) in Pb-Pb collisions at a center-of-mass energy ( √sNN ) of 2.76 TeV with the ALICE detector. ρ 00 values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum ( p T < 2 GeV / c ) for K*0 and ϕ at a level of 3 σ and 2 σ , respectively. No significant spin alignment is observed for the K0S meson ( spin = 0 ) in Pb-Pb collisions and for the vector mesons in p p collisions. The measured spin alignment is unexpectedly large but qualitatively consistent with the expectation from models which attribute it to a polarization of quarks in the presence of angular momentum in heavy-ion collisions and a subsequent hadronization by the process of recombination.
Abstract
To operate the ALICE Time Projection Chamber in continuous mode during the Run 3 and Run 4 data-taking periods of the Large Hadron Collider, the multi-wire proportional chamber-based readout ...was replaced with gas-electron multipliers. As expected, the detector performance is affected by the so-called common-mode effect, which leads to significant baseline fluctuations. A detailed study of the pulse shape with the new readout has revealed that it is also affected by ion tails. Since reconstruction and data compression are performed fully online, these effects must be corrected at the hardware level in the FPGA-based common readout units. The characteristics of the common-mode effect and of the ion tail, as well as the algorithms developed for their online correction, are described in this paper. The common-mode dependencies are studied using machine-learning techniques. Toy Monte Carlo simulations are performed to illustrate the importance of online corrections and to investigate the performance of the developed algorithms.
The production of the
Λ
(1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at
s
=
7
TeV
and in p–Pb collisions at
s
NN
=
5.02
TeV
for non-single diffractive events ...and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel
Λ
(1520)
→
pK
-
and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p–Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (
π
, K,
K
S
0
, p,
Λ
) describes the shape of the
Λ
(1520) transverse momentum distribution up to
3.5
GeV
/
c
in p–Pb collisions. In the framework of this model, this observation suggests that the
Λ
(1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of
Λ
(
1520
)
to the yield of the ground state particle
Λ
remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p–Pb collisions on the
Λ
(1520) yield.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Invariant differential yields of deuterons and antideuterons in pp collisions at s = 0.9, 2.76 and 7 TeV and the yields of tritons, He3 nuclei, and their antinuclei at s = 7 TeV have been measured ...with the ALICE detector at the CERN Large Hadron Collider. The measurements cover a wide transverse momentum (pT) range in the rapidity interval |y|
The multiplicity dependence of electron production from heavy-flavour hadron decays as a function of transverse momentum was measured in p-Pb collisions at
s
NN
= 5
.
02 TeV using the ALICE detector ...at the LHC. The measurement was performed in the centre-of-mass rapidity interval
−
1
.
07
< y
cms
<
0
.
14 and transverse momentum interval 2
< p
T
<
16 GeV
/c
. The multiplicity dependence of the production of electrons from heavy-flavour hadron decays was studied by comparing the
p
T
spectra measured for different multiplicity classes with those measured in pp collisions (
Q
pPb
) and in peripheral p-Pb collisions (
Q
cp
). The
Q
pPb
results obtained are consistent with unity within uncertainties in the measured
p
T
interval and event classes. This indicates that heavy-flavour decay electron production is consistent with binary scaling and independent of the geometry of the collision system. Additionally, the results suggest that cold nuclear matter effects are negligible within uncertainties, in the production of heavy-flavour decay electrons at midrapidity in p-Pb collisions.
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