A
bstract
Measurements of the production of electrons from heavy-flavour hadron decays in pp collisions at
s
= 13 TeV at midrapidity with the ALICE detector are presented down to a transverse ...momentum (
p
T
) of 0.2 GeV/
c
and up to
p
T
= 35 GeV/
c
, which is the largest momentum range probed for inclusive electron measurements in ALICE. In p-Pb collisions, the production cross section and the nuclear modification factor of electrons from heavy-flavour hadron decays are measured in the
p
T
range 0
.
5
< p
T
<
26 GeV/
c
at
s
NN
= 8
.
16 TeV. The nuclear modification factor is found to be consistent with unity within the statistical and systematic uncertainties. In both collision systems, first measurements of the yields of electrons from heavy-flavour hadron decays in different multiplicity intervals normalised to the multiplicity-integrated yield (self-normalised yield) at midrapidity are reported as a function of the self-normalised charged-particle multiplicity estimated at midrapidity. The self-normalised yields in pp and p-Pb collisions grow faster than linear with the self-normalised multiplicity. A strong
p
T
dependence is observed in pp collisions, where the yield of high-
p
T
electrons increases faster as a function of multiplicity than the one of low-
p
T
electrons. The measurement in p-Pb collisions shows no
p
T
dependence within uncertainties. The self-normalised yields in pp and p-Pb collisions are compared with measurements of other heavy-flavour, light-flavour, and strange particles, and with Monte Carlo simulations.
A
bstract
The Chiral Magnetic Wave (CMW) phenomenon is essential to provide insights into the strong interaction in QCD, the properties of the quark-gluon plasma, and the topological characteristics ...of the early universe, offering a deeper understanding of fundamental physics in high-energy collisions. Measurements of the charge-dependent anisotropic flow coefficients are studied in Pb-Pb collisions at center-of-mass energy per nucleon-nucleon collision
s
NN
= 5
.
02 TeV to probe the CMW. In particular, the slope of the normalized difference in elliptic (
v
2
) and triangular (
v
3
) flow coefficients of positively and negatively charged particles as a function of their event-wise normalized number difference, is reported for inclusive and identified particles. The slope
r
3
Norm
is found to be larger than zero and to have a magnitude similar to
r
2
Norm
, thus pointing to a large background contribution for these measurements. Furthermore,
r
2
Norm
can be described by a blast wave model calculation that incorporates local charge conservation. In addition, using the event shape engineering technique yields a fraction of CMW (
f
CMW
) contribution to this measurement which is compatible with zero. This measurement provides the very first upper limit for
f
CMW
, and in the 10–60% centrality interval it is found to be 26% (38%) at 95% (99.7%) confidence level.
The inclusive production of the charm–strange baryon Ωc0 is measured for the first time via its hadronic decay into Ω−π+ at midrapidity (|y|<0.5) in proton–proton (pp) collisions at the ...centre-of-mass energy s=13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2<pT<12GeV/c. The pT dependence of the Ωc0-baryon production relative to the prompt D0-meson and to the prompt Ξc0-baryon production is compared to various models that take different hadronisation mechanisms into consideration. In the measured pT interval, the ratio of the pT-integrated cross sections of Ωc0 and prompt Λc+ baryons multiplied by the Ω−π+ branching ratio is found to be larger by a factor of about 20 with a significance of about 4σ when compared to e+e− collisions.
A
bstract
Measurements of charged-particle production in pp, p–Pb, and Pb–Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined ...event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum
p
T
trig
in the range 8
<
p
T
trig
<
15 GeV
/c
. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial- and final-state radiation. The relative transverse activity classifier,
R
T
=
N
ch
T
/
N
ch
T
, is used to group events according to their UE activity, where
N
ch
T
is the charged-particle multiplicity per event in the transverse region and
N
ch
T
is the mean value over the whole analysed sample. The energy dependence of the
R
T
distributions in pp collisions at
s
= 2
.
76, 5.02, 7, and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions. The first measurements of charged-particle
p
T
spectra as a function of
R
T
in the three azimuthal regions in pp, p–Pb, and Pb–Pb collisions at
s
NN
= 5
.
02 TeV are also reported. Data are compared with predictions obtained from the event generators PYTHIA 8 and EPOS LHC. This set of measurements is expected to contribute to the understanding of the origin of collective-like effects in small collision systems (pp and p–Pb).
Analog readout modules for the ZEUS microvertex detector Fusayasu, T.; Tokushuku, K.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/1999, Letnik:
436, Številka:
1
Journal Article
Recenzirano
Analog readout modules have been developed for a silicon microvertex detector of the electron–proton collision experiment ZEUS. Analog signals kept in the front end are read out and digitized by ADCs ...and processed afterwards to reduce the data volume while keeping the signal information. We have developed prototype modules with 10-bit 10
MHz ADCs and digital processors built in Field Programmable Gate Arrays. Their performance was investigated.
We have developed a novel technique for the measurement of the avalanche fluctuation of gaseous detectors using a UV laser. The technique is simple and requires a short data-taking time of about ten ...minutes. Furthermore, it is applicable for relatively low gas gains. Our experimental setup as well as the measurement principle, and the results obtained with a stack of Gas Electron Multipliers (GEMs) operated in several gas mixtures are presented.
Abstract
Hadronic resonances are used to probe the hadron gas produced in the late stage of heavy-ion collisions since they decay on the same timescale, of the order of 1–10 fm/
c
, as the decoupling ...time of the system. In the hadron gas, (pseudo)elastic scatterings among the products of resonances that decayed before the kinetic freeze-out and regeneration processes counteract each other, the net effect depending on the resonance lifetime, the duration of the hadronic phase, and the hadronic cross sections at play. In this context, the
$$\Sigma (1385)^{\pm }$$
Σ
(
1385
)
±
particle is of particular interest as models predict that regeneration dominates over rescattering despite its relatively short lifetime of about 5.5 fm/
c
. The first measurement of the
$$\Sigma (1385)^{\pm }$$
Σ
(
1385
)
±
resonance production at midrapidity in Pb–Pb collisions at
$$\sqrt{s_{\textrm{NN}}}= 5.02$$
s
NN
=
5.02
TeV with the ALICE detector is presented in this Letter. The resonances are reconstructed via their hadronic decay channel,
$$\Lambda \pi $$
Λ
π
, as a function of the transverse momentum (
$$p_\textrm{T}$$
p
T
) and the collision centrality. The results are discussed in comparison with the measured yield of pions and with expectations from the statistical hadronization model as well as commonly employed event generators, including PYTHIA8/Angantyr and EPOS3 coupled to the UrQMD hadronic cascade afterburner. None of the models can describe the data. For
$$\Sigma (1385)^{\pm }$$
Σ
(
1385
)
±
, a similar behaviour as
$$\textrm{K}^{*} (892)^{0}$$
K
∗
(
892
)
0
is observed in data unlike the predictions of EPOS3 with afterburner.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The interaction of
$$\textrm{K}^{-}$$
K
-
with protons is characterised by the presence of several coupled channels, systems like
$${\overline{\textrm{K}}}^0$$
K
¯
0
n and
$$\uppi \Sigma $$
...π
Σ
with a similar mass and the same quantum numbers as the
$$\textrm{K}^{-}$$
K
-
p state. The strengths of these couplings to the
$$\textrm{K}^{-}$$
K
-
p system are of crucial importance for the understanding of the nature of the
$$\Lambda (1405)$$
Λ
(
1405
)
resonance and of the attractive
$$\textrm{K}^{-}$$
K
-
p strong interaction. In this article, we present measurements of the
$$\textrm{K}^{-}$$
K
-
p correlation functions in relative momentum space obtained in pp collisions at
$$\sqrt{s}~=~13$$
s
=
13
Te, in p–Pb collisions at
$$\sqrt{s_{\textrm{NN}}}~=~5.02$$
s
NN
=
5.02
Te, and (semi)peripheral Pb–Pb collisions at
$$\sqrt{s_{\textrm{NN}}}~=~5.02$$
s
NN
=
5.02
Te. The emitting source size, composed of a core radius anchored to the
$$\textrm{K}^{+}$$
K
+
p correlation and of a resonance halo specific to each particle pair, varies between 1 and 2 fm in these collision systems. The strength and the effects of the
$${\overline{\textrm{K}}}^0$$
K
¯
0
n and
$$\uppi \Sigma $$
π
Σ
inelastic channels on the measured
$$\textrm{K}^{-}$$
K
-
p correlation function are investigated in the different colliding systems by comparing the data with state-of-the-art models of chiral potentials. A novel approach to determine the conversion weights
$$\omega $$
ω
, necessary to quantify the amount of produced inelastic channels in the correlation function, is presented. In this method, particle yields are estimated from thermal model predictions, and their kinematic distribution from blast-wave fits to measured data. The comparison of chiral potentials to the measured
$$\textrm{K}^{-}$$
K
-
p interaction indicates that, while the
$$\uppi \Sigma $$
π
Σ
–
$$\textrm{K}^{-}$$
K
-
p dynamics is well reproduced by the model, the coupling to the
$${\overline{\textrm{K}}}^0$$
K
¯
0
n channel in the model is currently underestimated.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The performance of the jet trigger for the ATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton–proton collisions with a centre-of-mass ...energy of 7 TeV and heavy ion collisions with a 2.76 TeV per nucleon–nucleon collision energy. The ATLAS trigger is a three level system designed to reduce the rate of events from the 40 MHz nominal maximum bunch crossing rate to the approximate 400 Hz which can be written to offline storage. The ATLAS jet trigger is the primary means for the online selection of events containing jets. Events are accepted by the trigger if they contain one or more jets above some transverse energy threshold. During 2011 data taking the jet trigger was fully efficient for jets with transverse energy above 25 GeV for triggers seeded randomly at Level 1. For triggers which require a jet to be identified at each of the three trigger levels, full efficiency is reached for offline jets with transverse energy above 60 GeV. Jets reconstructed in the final trigger level and corresponding to offline jets with transverse energy greater than 60 GeV, are reconstructed with a resolution in transverse energy with respect to offline jets, of better than 4 % in the central region and better than 2.5 % in the forward direction.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable B-Layer, a new ...innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity s=13 TeV pp collision sample corresponding to around 2.0 nb−1 collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation.
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