Abstract
The technique of material budget imaging (MBI) allows to experimentally assess the material budget
ϵ
=
x
/
X
0
of a material with thickness
x
and its radiation length
X
0
. Here, multi-GeV ...electrons from a test beam facility such as the DESY-II test beam are used. This novel technique exploits the fact that the beam particles are deflected by multiple Coulomb scattering following a distribution of the deflection angle with a center at zero and a width depending on the traversed material. By reconstructing the individual kink angles from the measured particle trajectories in a high resolution beam telescope, the material budget can be extracted by applying appropriate models of multiple scattering theory, such as the Highland formula.
On the one hand, various materials with known material budgets were measured to calibrate the MBI technique and study also different systematic effects such as the beam telescope’s acceptance and the variation of the beam energy. On the other hand, a number of material samples planned in the design of the local support structures of the new ATLAS Inner Tracker (ITk) strip detector were investigated to extract the according radiation length values not known beforehand.
This paper shows therefore the potential of the MBI technique to give an input for the design of high-energy particle detectors by providing experimentally measured numbers of the radiation length for various material compounds with not a-priori known
X
0
values.
EUTelescope is a modular, comprehensive software framework for the reconstruction of particle trajectories recorded with beam telescopes. Its modularity allows for a flexible usage of processors each ...fulfilling separate tasks of the reconstruction chain such as clustering, alignment and track fitting. The framework facilitates the usage of any position sensitive device for both the beam telescope sensors as well as the device under test and supports a wide range of geometric arrangements of the sensors. In this work, the functionality of the EUTelescope framework as released in v2.2 and its underlying dependencies are discussed. Various use cases with emphasis on the General Broken Lines advanced track fitting methods give examples of the work flow and capabilities of the framework.
Abstract
This study is focused on an investigation of the performance
of the Short Strip module developed by the ATLAS Inner Tracker (ITk)
strip collaboration using electron beams of energy 5.4 GeV ...and
5.8 GeV at the DESY-II Testbeam Facility. The noise at
+30 °C and -30 °C was
measured. The ratio of the two measurements is compared with a
circuit-model calculation. The measured noise at
-30 °C is compared with the maximum noise that
would correspond to an acceptable signal-to-noise ratio after the
expected radiation damage from operation at HL-LHC. The measured
charge distributions at +30 °C and
-30 °C are compared with GEANT4 simulations. The
detection efficiency and noise-occupancy were measured as a function
of threshold at both +30 °C and
-30 °C. The average cluster width was measured
as a function of threshold. Scans of detection efficiency versus
threshold at different delay settings were used to reconstruct the
pulse shape in time. The resulting pulse shape was compared with a
circuit model calculation.
EUDAQ is a generic data acquisition software developed for use in conjunction with common beam telescopes at charged particle beam lines. Providing high-precision reference tracks for performance ...studies of new sensors, beam telescopes are essential for the research and development towards future detectors for high-energy physics. As beam time is a highly limited resource, EUDAQ has been designed with reliability and ease-of-use in mind. It enables flexible integration of different independent devices under test via their specific data acquisition systems into a top-level framework. EUDAQ controls all components globally, handles the data flow centrally and synchronises and records the data streams. Over the past decade, EUDAQ has been deployed as part of a wide range of successful test beam campaigns and detector development applications.
This paper presents the observation of four-top-quark (
t
t
¯
t
t
¯
) production in proton-proton collisions at the LHC. The analysis is performed using an integrated luminosity of 140
fb
-
1
at a ...centre-of-mass energy of 13 TeV collected using the ATLAS detector. Events containing two leptons with the same electric charge or at least three leptons (electrons or muons) are selected. Event kinematics are used to separate signal from background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The observed (expected) significance of the measured
t
t
¯
t
t
¯
signal with respect to the standard model (SM) background-only hypothesis is 6.1 (4.3) standard deviations. The
t
t
¯
t
t
¯
production cross section is measured to be
22
.
5
-
5.5
+
6.6
fb, consistent with the SM prediction of
12.0
±
2.4
fb within 1.8 standard deviations. Data are also used to set limits on the three-top-quark production cross section, being an irreducible background not measured previously, and to constrain the top-Higgs Yukawa coupling and effective field theory operator coefficients that affect
t
t
¯
t
t
¯
production.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
Measurements of the production cross-sections of the Standard Model (SM) Higgs boson (
H
) decaying into a pair of
τ
-leptons are presented. The measurements use data collected with the ...ATLAS detector from
pp
collisions produced at the Large Hadron Collider at a centre-of-mass energy of
s
= 13 TeV, corresponding to an integrated luminosity of 139 fb
−
1
. Leptonic (
τ
→
ℓν
ℓ
ν
τ
) and hadronic (
τ
→ hadrons
ν
τ
) decays of the
τ
-lepton are considered. All measurements account for the branching ratio of
H → ττ
and are performed with a requirement
|y
H
| <
2
.
5, where
y
H
is the true Higgs boson rapidity. The cross-section of the
pp → H → ττ
process is measured to be 2
.
94
±
0.21
stat
−
0.32
+
0.37
(syst) pb, in agreement with the SM prediction of 3
.
17
±
0
.
09 pb. Inclusive cross-sections are determined separately for the four dominant production modes: 2
.
65
±
0.41
stat
−
0.67
+
0.91
(syst) pb for gluon-gluon fusion, 0
.
197
±
0.028
stat
−
0.026
+
0.032
(syst) pb for vector-boson fusion, 0
.
115
±
0.058
stat
−
0.040
+
0.042
(syst) pb for vector-boson associated production, and 0
.
033
±
0.031
stat
−
0.017
+
0.022
(syst) pb for top-quark pair associated production. Measurements in exclusive regions of the phase space, using the simplified template cross-section framework, are also performed. All results are in agreement with the SM predictions.
A
bstract
The associated production of a Higgs boson and a top-quark pair is measured in events characterised by the presence of one or two electrons or muons. The Higgs boson decay into a
b
-quark ...pair is used. The analysed data, corresponding to an integrated luminosity of 139 fb
−
1
, were collected in proton-proton collisions at the Large Hadron Collider between 2015 and 2018 at a centre-of-mass energy of
s
= 13 TeV. The measured signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model, is
0.35
−
0.34
+
0.36
. This result is compatible with the Standard Model prediction and corresponds to an observed (expected) significance of 1.0 (2.7) standard deviations. The signal strength is also measured differentially in bins of the Higgs boson transverse momentum in the simplified template cross-section framework, including a bin for specially selected boosted Higgs bosons with transverse momentum above 300 GeV.
The first evidence for the Higgs boson decay to a Z boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the ...searches performed by the ATLAS and CMS Collaborations with proton-proton collision datasets collected at the CERN Large Hadron Collider (LHC) from 2015 to 2018. These correspond to integrated luminosities of around 140 fb^{-1} for each experiment, at a center-of-mass energy of 13 TeV. The measured signal yield is 2.2±0.7 times the standard model prediction, and agrees with the theoretical expectation within 1.9 standard deviations.
The planned High Luminosity Large Hadron Collider is being designed to maximise the physics potential of the LHC with 10 years of operation at instantaneous luminosities of 7.5×1034cm−2s−1. A ...consequence of this increased luminosity is the expected radiation damage requiring the tracking detectors to withstand hadron fluence to over 1×1015 1 MeV neutron equivalent per cm2 in the ATLAS Strips system. Fast readout electronics, deploying 130 nm CMOS front-end electronics are glued on top of a silicon sensor to make a module. The radiation hard n-in-p micro-strip sensors used have been developed by the ATLAS ITk Strip Sensor collaboration and produced by Hamamatsu Photonics. A series of tests were performed at the DESY-II test beam facility to investigate the detailed performance of a strip module with both 2.5 cm and 5 cm length strips before irradiation. The DURANTA telescope was used to obtain a pointing resolution of 2 μm, with an additional pixel layer installed to improve timing resolution to ∼25 ns. Results show that prior to irradiation a wide range of thresholds (0.5–2.0 fC) meet the requirements of a noise occupancy less than 1×10−3 and a hit efficiency greater than 99%.
This paper presents the muon momentum calibration and performance studies for the ATLAS detector based on the
pp
collisions data sample produced at
s
= 13 TeV at the LHC during Run 2 and ...corresponding to an integrated luminosity of 139
fb
-
1
. An innovative approach is used to correct for potential charge-dependent momentum biases related to the knowledge of the detector geometry, using the
Z
→
μ
+
μ
-
resonance. The muon momentum scale and resolution are measured using samples of
J
/
ψ
→
μ
+
μ
-
and
Z
→
μ
+
μ
-
events. A calibration procedure is defined and applied to simulated data to match the performance measured in real data. The calibration is validated using an independent sample of
Υ
→
μ
+
μ
-
events. At the
Z
(
J
/
ψ
)
peak, the momentum scale is measured with an uncertainty at the 0.05% (0.1%) level, and the resolution is measured with an uncertainty at the 1.5% (2%) level. The charge-dependent bias is removed with a dedicated in situ correction for momenta up to 450 GeV with a precision better than 0.03
TeV
-
1
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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