An improved Shashlyk calorimeter Atoian, G.S.; Britvich, G.I.; Chernichenko, S.K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2008, Letnik:
584, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Shashlyk electromagnetic calorimeter modules with an energy resolution of about
3
%
/
E
(
GeV
)
for
50
–
1000
MeV
photons have been developed, and a prototype tested. Details of these improved ...modules, including mechanical construction, selection of wave shifting fibers and photo-detectors, and development of a new scintillator with improved optical and mechanical properties are described. How the modules will perform in a large calorimeter was determined from prototype measurements. The experimentally determined characteristics of the calorimeter prototype show energy resolution of
σ
E
/
E
=
(
1.96
±
0.1
)
%
⊕
(
2.74
±
0.05
)
%
/
E
, time resolution of
σ
T
=
(
72
±
4
)
/
E
⊕
(
14
±
2
)
/
E
(
ps
)
, where photon energy
E is given in GeV units and
⊕
means a quadratic summation. A punch-through inefficiency of photon detection was measured to be
ε
≈
5
×
10
-
5
(
Θ
beam
>
5
mrad
)
.
Prototype of the fast timing Cherenkov detector, applicable in high-energy collider experiments, has been developed basing on the modified Planacon XP85012 MCP-PMT and fused silica radiators. We ...present the reasons and description of the MCP-PMT modification, timing and amplitude characteristics of the prototype including the summary of the detector's response on particle hits at oblique angles and MCP-PMT performance at high illumination rates.
A
bstract
The production of prompt charmed mesons D
0
, D
+
and D
∗+
, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the centre-of-mass energy per nucleon pair,
...s
N
N
, of 2
.
76 TeV. The production yields for rapidity |
y
|
<
0
.
5 are presented as a function of transverse momentum,
p
T
, in the interval 1–36 GeV
/c
for the centrality class 0–10% and in the interval 1–16 GeV
/c
for the centrality class 30–50%. The nuclear modification factor
R
AA
was computed using a proton-proton reference at
s
=
2.76
TeV, based on measurements at
s
=
7
TeV and on theoretical calculations. A maximum suppression by a factor of 5-6 with respect to binary-scaled pp yields is observed for the most central collisions at
p
T
of about 10 GeV
/c
. A suppression by a factor of about 2-3 persists at the highest
p
T
covered by the measurements. At low
p
T
(1-3 GeV
/c
), the
R
AA
has large uncertainties that span the range 0.35 (factor of about 3 suppression) to 1 (no suppression). In all
p
T
intervals, the
R
AA
is larger in the 30-50% centrality class compared to central collisions. The D-meson
R
AA
is also compared with that of charged pions and, at large
p
T
, charged hadrons, and with model calculations.
A
bstract
Production of inclusive charmonia in pp collisions at center-of-mass energy of
s
= 13 TeV and p–Pb collisions at center-of-mass energy per nucleon pair of
s
NN
= 8
.
16 TeV is studied as a ...function of charged-particle pseudorapidity density with ALICE. Ground and excited charmonium states (
J/ψ
,
ψ
(2S)) are measured from their dimuon decays in the interval of rapidity in the center-of-mass frame 2
.
5
< y
cms
<
4
.
0 for pp collisions, and 2
.
03
< y
cms
<
3
.
53 and −4
.
46
< y
cms
<
−2
.
96 for p–Pb collisions. The charged-particle pseudorapidity density is measured around midrapidity (|
η
|
<
1
.
0). In pp collisions, the measured charged-particle multiplicity extends to about six times the average value, while in p-Pb collisions at forward (backward) rapidity a multiplicity corresponding to about three (four) times the average is reached. The
ψ
(2S) yield increases with the charged-particle pseudorapidity density. The ratio of
ψ
(2S) over
J/ψ
yield does not show a significant multiplicity dependence in either colliding system, suggesting a similar behavior of
J/ψ
and
ψ
(2S) yields with respect to charged-particle pseudorapidity density. Results for the
ψ
(2S) yield and its ratio with respect to
J/ψ
agree with available model calculations.
Development of Shashlyk calorimeter for KOPIO Atoian, G.S.; Issakov, V.V.; Karavichev, O.V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2004, Letnik:
531, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A large size electromagnetic calorimeter with an energy resolution of
3%/
E
(
GeV)
for 100–
500
MeV
photons is one of the keystone elements of the KOPIO experiment. In this paper we describe the ...method of optimization of the Shashlyk module to achieve the required energy resolution. To optimize the calorimeter module design, a model for simulation of the energy resolution was developed. It includes the effects of shower evolution, light collection in scintillator plates, light attenuation in fibers, quantum efficiency of the photo-detector, threshold and noise in the readout system. This model was adjusted using the results of a 0.5–
2
GeV/c
positron test beam study of a calorimeter prototype with an energy resolution of
4%/
E
(
GeV)
. Possible improvements of the Shashlyk energy resolution to
3%/
E
(
GeV)
, the level required by KOPIO experiment, are discussed.
A
bstract
The production of strange hadrons (
K
S
0
, Λ, Ξ
±
, and Ω
±
), baryon-to-meson ratios (Λ
/
K
S
0
, Ξ
/
K
S
0
, and Ω
/
K
S
0
), and baryon-to-baryon ratios (Ξ
/
Λ, Ω
/
Λ, and Ω
/
Ξ) ...associated with jets and the underlying event were measured as a function of transverse momentum (
p
T
) in pp collisions at
s
= 13 TeV and p Pb collisions at
s
NN
= 5
.
02 TeV with the ALICE detector at the LHC. The inclusive production of the same particle species and the corresponding ratios are also reported. The production of multi-strange hadrons, Ξ
±
and Ω
±
, and their associated particle ratios in jets and in the underlying event are measured for the first time. In both pp and p–Pb collisions, the baryon-to-meson and baryon-to-baryon yield ratios measured in jets differ from the inclusive particle production for low and intermediate hadron
p
T
(0.6–6 GeV/
c
). Ratios measured in the underlying event are in turn similar to those measured for inclusive particle production. In pp collisions, the particle production in jets is compared with P
ythia
8 predictions with three colour-reconnection implementation modes. None of them fully reproduces the data in the measured hadron
p
T
region. The maximum deviation is observed for Ξ
±
and Ω
±
which reaches a factor of about six. The event multiplicity dependence is further investigated in p−Pb collisions. In contrast to what is observed in the underlying event, there is no significant event-multiplicity dependence for particle production in jets. The presented measurements provide novel constraints on hadronisation and its Monte Carlo description. In particular, they demonstrate that the fragmentation of jets alone is insufficient to describe the strange and multi-strange particle production in hadronic collisions at LHC energies.
Understanding the role of parton mass and Casimir color factors in the quantum chromodynamics parton shower represents an important step in characterizing the emission properties of heavy quarks. ...Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterize gluon emissions from heavy quarks. In this Letter, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed D^{0} meson. The measurement is made in proton-proton collisions at sqrts=13 TeV, in the low jet transverse-momentum interval of 15≤p_{T}^{jet ch}<30 GeV/c where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, is reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared with gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions.
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