Two modules of the AD detector have been studied with the test beam at the T10 facility at CERN. The AD detector is made of scintillator pads read out by wave-length shifters (WLS) coupled to clean ...fibres that carry the produced light to photo-multiplier tubes (PMTs). In ALICE the AD is used to trigger and study the physics of diffractive and ultra-peripheral collisions as well as for a variety of technical tasks like beam-gas background monitoring or as a luminometer. \par The position dependence of the modules' efficiency has been measured and the effect of hits on the WLS or PMTs has been evaluated. The charge deposited by pions and protons has been measured at different momenta of the test beam. The time resolution is determined as a function of the deposited charge. These results are important ingredients to better understand the AD detector, to benchmark the corresponding simulations, and very importantly they served as a baseline for a similar device, the Forward Diffractive Detector (FDD), being currently built and that will be in operation in ALICE during the LHC Runs 3 and 4.
A beam–beam monitoring detector for the MPD experiment at NICA Alvarado, Mauricio; Ayala, Alejandro; Ayala-Torres, Marco Alberto ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Letnik:
953
Journal Article
Recenzirano
Odprti dostop
The Multi-Purpose Detector (MPD) is to be installed at the Nuclotron Ion Collider fAcility (NICA) of the Joint Institute for Nuclear Research (JINR). Its main goal is to study the phase diagram of ...the strongly interacting matter produced in heavy-ion collisions. These studies, while providing insight into the physics of heavy-ion collisions, are relevant for improving our understanding of the evolution of the early Universe and the formation of neutron stars. In order to extend the MPD trigger capabilities, we propose to include a high granularity beam–beam monitoring detector (BE–BE) to provide a level-0 trigger signal with an expected time resolution of 30 ps. This new detector will improve the determination of the reaction plane by the MPD experiment, a key measurement for flow studies that provides physics insight into the early stages of the reaction.
In this work, we use simulated Au+Au collisions at NICA energies to show the potential of such a detector to determine the event plane resolution, providing further redundancy to the detectors originally considered for this purpose namely, the Fast Forward Detector (FFD) and the Hadron Calorimeter (HCAL). We also show our results for the time resolution studies of two prototype cells carried out at the T10 beam line at the CERN PS complex.
LHC forward physics Akiba, K; Baillie, O Villalobos; Baus, C ...
Journal of physics. G, Nuclear and particle physics,
2016, Letnik:
43, Številka:
11
Journal Article
Recenzirano
Odprti dostop
The goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a ...selection of the Monte Carlo simulation tools currently available, chapter 2, then enters the rich phenomenology of QCD at low, chapter 3, and high, chapter 4, momentum transfer, while the unique scattering conditions of central exclusive production are analyzed in chapter 5. The last two experimental topics, Cosmic Ray and Heavy Ion physics are presented in the chapter 6 and 7 respectively. Chapter 8 is dedicated to the BFKL dynamics, multiparton interactions, and saturation. Here, the report ends with an overview of the forward detectors at LHC. Each chapter is correlated with a comprehensive bibliography, attempting to provide to the interested reader with a wide opportunity for further studies.
The production cross sections for prompt charmed mesons
D
0
,
D
+
,
D
∗
+
and
D
s
+
were measured at mid-rapidity in proton–proton collisions at a centre-of-mass energy
s
=
7
TeV
with the ALICE ...detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays
D
0
→
K
-
π
+
,
D
+
→
K
-
π
+
π
+
,
D
∗
+
→
D
0
π
+
,
D
s
+
→
ϕ
π
+
→
K
-
K
+
π
+
, and their charge conjugates.With respect to previous measurements in the same rapidity region, the coverage in transverse momentum (
p
T
) is extended and the uncertainties are reduced by a factor of about two. The accuracy on the estimated total
c
c
¯
production cross section is likewise improved. The measured
p
T
-differential cross sections are compared with the results of three perturbative QCD calculations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
Inclusive J
/ψ
production is studied in minimum-bias proton-proton collisions at a centre-of-mass energy of
s
= 5
.
02 TeV by ALICE at the CERN LHC. The measurement is performed at ...mid-rapidity (
|y| <
0
.
9) in the dielectron decay channel down to zero transverse momentum
p
T
, using a data sample corresponding to an integrated luminosity of
L
int
= 19
.
4
±
0
.
4 nb
−
1
. The measured
p
T
-integrated inclusive J
/ψ
production cross sec- tion is d
σ/
d
y
= 5
.
64
±
0
.
22(stat.)
±
0
.
33(syst.)
±
0
.
12(lumi.)
μ
b. The
p
T
-differential cross section d
2
σ/
d
p
T
d
y
is measured in the
p
T
range 0–10 GeV
/c
and compared with state-of- the-art QCD calculations. The J
/ψ
〈
p
T
〉 and
p
T
2
are extracted and compared with results obtained at other collision energies.
We present the charged-particle multiplicity distributions over a wide pseudorapidity range (
-
3.4
<
η
<
5.0
) for pp collisions at
s
=
0.9
,
7
, and 8 TeV at the LHC. Results are based on ...information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE, extending the pseudorapidity coverage of the earlier publications and the high-multiplicity reach. The measurements are compared to results from the CMS experiment and to PYTHIA, PHOJET and EPOS LHC event generators, as well as IP-Glasma calculations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
The first measurement of e
+
e
−
pair production at mid-rapidity (|
η
e
| < 0.8) in pp collisions at
s
=
7
TeV with ALICE at the LHC is presented. The dielectron production is studied as a ...function of the invariant mass (
m
ee
< 3.3 GeV/
c
2
), the pair transverse momentum (
p
T,ee
< 8 GeV/
c
), and the pair transverse impact parameter (DCA
ee
), i.e., the average distance of closest approach of the reconstructed electron and positron tracks to the collision vertex, normalised to its resolution. The results are compared with the expectations from a cocktail of known hadronic sources and are well described when PYTHIA is used to generate the heavy-flavour contributions. In the low-mass region (0.14 <
m
ee
< 1.1 GeV/
c
2
), prompt and non-prompt e
+
e
−
sources can be separated via the DCA
ee
. In the intermediate-mass region (1.1 <
m
ee
< 2.7 GeV/
c
2
), a double-differential fit to the data in
m
ee
and
p
T,ee
and a fit of the DCA
ee
distribution allow the total
c
c
¯
and
b
b
¯
cross sections to be extracted. Two different event generators, PYTHIA and POWHEG, can reproduce the shape of the two-dimensional
m
ee
and
p
T,ee
spectra, as well as the shape of the DCA
ee
distribution, reasonably well. However, differences in the
c
c
¯
and
b
b
¯
cross sections are observed when using the generators to extrapolate to full phase space. Finally, the ratio of inclusive to decay photons is studied via the measurement of virtual direct photons in the transverse-momentum range 1 <
p
T
< 8 GeV/
c
. This is found to be unity within the statistical and systematic uncertainties and consistent with expectations from next-to-leading order perturbative quantum chromodynamic calculations.
A
bstract
Production cross sections of muons from semi-leptonic decays of charm and beauty hadrons were measured at forward rapidity (2
.
5
< y <
4) in proton-proton (pp) collisions at a ...centre-of-mass energy
s
= 5
.
02 TeV with the ALICE detector at the CERN LHC. The results were obtained in an extended transverse momentum interval, 2
< p
T
<
20 GeV/
c
, and with an improved precision compared to previous measurements performed in the same rapidity interval at centre-of-mass energies
s
= 2
.
76 and 7 TeV. The
p
T
- and
y
-differential production cross sections as well as the
p
T
-differential production cross section ratios between different centre-of-mass energies and different rapidity intervals are described, within experimental and theoretical uncertainties, by predictions based on perturbative QCD.
A
bstract
Two-particle correlations in high-energy collision experiments enable the extraction of particle source radii by using the Bose-Einstein enhancement of pion production at low relative ...momentum
q
∝ 1/
R
. It was previously observed that in pp collisions at
s
= 7TeV the average pair transverse momentum
k
T
range of such analyses is limited due to large background correlations which were attributed to mini-jet phenomena. To investigate this further, an event-shape dependent analysis of Bose-Einstein correlations for pion pairs is performed in this work. By categorizing the events by their transverse sphericity
S
T
into spherical (
S
T
> 0:7) and jet-like (
S
T
< 0:3) events a method was developed that allows for the determination of source radii for much larger values of
k
T
for the first time. Spherical events demonstrate little or no background correlations while jet-like events are dominated by them. This observation agrees with the hypothesis of a mini-jet origin of the non-femtoscopic background correlations and gives new insight into the physics interpretation of the
k
T
dependence of the radii. The emission source size in spherical events shows a substantially diminished
k
T
dependence, while jet-like events show indications of a negative trend with respect to
k
T
in the highest multiplicity events. Regarding the emission source shape, the correlation functions for both event sphericity classes show good agreement with an exponential shape, rather than a Gaussian one.
A
bstract
The production of charm jets in proton-proton collisions at a center-of-mass energy of
s
=
7
TeV was measured with the ALICE detector at the CERN Large Hadron Collider. The measurement is ...based on a data sample corresponding to a total integrated luminosity of 6
.
23 nb
−1
, collected using a minimum-bias trigger. Charm jets are identified by the presence of a D
0
meson among their constituents. The D
0
mesons are reconstructed from their hadronic decay D
0
→K
−
π
+
. The D
0
-meson tagged jets are reconstructed using tracks of charged particles (track-based jets) with the anti-
k
T
algorithm in the jet transverse momentum range
5
<
p
T
,
jet
ch
<
30 GeV
/c
and pseudorapidity |
η
jet
|
<
0
.
5. The fraction of charged jets containing a D
0
-meson increases with
p
T
,
jet
ch
from 0
.
042 ± 0
.
004 (stat) ± 0
.
006 (syst) to 0
.
080 ± 0
.
009 (stat) ± 0
.
008 (syst). The distribution of D
0
-meson tagged jets as a function of the jet momentum fraction carried by the D
0
meson in the direction of the jet axis
z
∥
ch
is reported for two ranges of jet transverse momenta,
5
<
p
T
,
jet
ch
<
15 GeV
/c
and
15
<
p
T
,
jet
ch
<
30 GeV
/c
in the intervals
0.2
<
z
‖
ch
<
1.0
and
0.4
<
z
‖
ch
<
1.0
, respectively. The data are compared with results from Monte Carlo event generators (PYTHIA 6, PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum Chromodynamics calculation, obtained with the POWHEG method and interfaced with PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation and underlying event.
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