During withdrawal from cocaine, calcium permeable-AMPA receptors (CP-AMPAR) progressively accumulate in nucleus accumbens (NAc) synapses, a phenomenon linked to behavioral sensitization and ...drug-seeking. Recently, it has been suggested that neuroimmune alterations might promote aberrant changes in synaptic plasticity, thus contributing to substance abuse-related behaviors. Here, we investigated the role of microglia in NAc neuroadaptations after withdrawal from cocaine-induced conditioned place preference (CPP). We depleted microglia using PLX5622-supplemented diet during cocaine withdrawal, and after the place preference test, we measured dendritic spine density and the presence of CP-AMPAR in the NAc shell. Microglia depletion prevented cocaine-induced changes in dendritic spines and CP-AMPAR accumulation. Furthermore, microglia depletion prevented conditioned hyperlocomotion without affecting drug-context associative memory. Microglia displayed fewer number of branches, resulting in a reduced arborization area and microglia control domain at late withdrawal. Our results suggest that microglia are necessary for the synaptic adaptations in NAc synapses during cocaine withdrawal and therefore represent a promising therapeutic target for relapse prevention.
The CMS collaboration considers upgrading the muon forward region which is particularly affected by the high-luminosity conditions at the LHC. The proposal involves Gas Electron Multiplier (GEM) ...chambers, which are able to handle the extreme particle rates expected in this region along with a high spatial resolution. This allows to combine tracking and triggering capabilities, which will improve the CMS muon High Level Trigger, the muon identification and the track reconstruction. Intense R&D has been going on since 2009 and it has lead to the development of several GEM prototypes and associated detector electronics. These GEM prototypes have been subjected to extensive tests in the laboratory and in test beams at the CERN Super Proton Synchrotron (SPS). This contribution will review the status of the CMS upgrade project with GEMs and its impact on the CMS performance.
A
bstract
A measurement of the inelastic proton-proton cross section with the CMS detector at a center-of-mass energy of
s
=
13
TeV is presented. The analysis is based on events with energy deposits ...in the forward calorimeters, which cover pseudorapidities of −6
.
6
< η <
−3
.
0 and +3
.
0
< η <
+5
.
2. An inelastic cross section of 68
.
6 ± 0
.
5(syst) ± 1
.
6(lumi) mb is obtained for events with
M
X
>
4
.
1 GeV and/or
M
Y
>
13 GeV, where
M
X
and
M
Y
are the masses of the diffractive dissociation systems at negative and positive pseudorapidities, respectively. The results are compared with those from other experiments as well as to predictions from high-energy hadron-hadron interaction models.
A
bstract
Properties of the Higgs boson are measured in the H → ZZ → 4ℓ (ℓ = e,
μ
) decay channel. A data sample of proton-proton collisions at
s
=
13
TeV, collected with the CMS detector at the LHC ...and corresponding to an integrated luminosity of 35.9 fb
−1
is used. The signal strength modifier
μ
, defined as the ratio of the observed Higgs boson rate in the H → ZZ → 4ℓ decay channel to the standard model expectation, is measured to be
μ
= 1.05
− 0.17
+ 0.19
at
m
H
= 125.09 GeV, the combined ATLAS and CMS measurement of the Higgs boson mass. The signal strength modifiers for the individual Higgs boson production modes are also measured. The cross section in the fiducial phase space defined by the requirements on lepton kinematics and event topology is measured to be 2. 92
− 0.44
+ 0.48
(stat)
− 0.24
+ 0.28
(syst)fb, which is compatible with the standard model prediction of 2.76 ± 0.14 fb. Differential cross sections are reported as a function of the transverse momentum of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet. The Higgs boson mass is measured to be
m
H
= 125.26 ± 0.21 GeV and the width is constrained using the on-shell invariant mass distribution to be Γ
H
< 1.10 GeV, at 95% confidence level.
New sets of parameters (“tunes”) for the underlying-event (UE) modelling of the
pythia
8,
pythia6
and
herwig++
Monte Carlo event generators are constructed using different parton distribution ...functions. Combined fits to CMS UE proton–proton (
p
p
) data at
s
=
7
TeV
and to UE proton–antiproton (
p
p
¯
) data from the CDF experiment at lower
s
, are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton–proton collisions at 13
TeV
. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to “minimum bias” (MB) events, multijet, and Drell–Yan (
q
q
¯
→
Z
/
γ
∗
→
lepton-antilepton+jets) observables at 7 and 8
TeV
, as well as predictions for MB and UE observables at 13
TeV
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The CMS muon detector system, muon reconstruction software, and high-level trigger underwent significant changes in 2013–2014 in preparation for running at higher LHC collision energy and ...instantaneous luminosity. The performance of the modified system is studied using proton-proton collision data at center-of-mass energy s=13 TeV, collected at the LHC in 2015 and 2016. The measured performance parameters, including spatial resolution, efficiency, and timing, are found to meet all design specifications and are well reproduced by simulation. Despite the more challenging running conditions, the modified muon system is found to perform as well as, and in many aspects better than, previously. We dedicate this paper to the memory of Prof. Alberto Benvenuti, whose work was fundamental for the CMS muon detector.
Many measurements and searches for physics beyond the standard model at the LHC rely on the efficient identification of heavy-flavour jets, i.e. jets originating from bottom or charm quarks. In this ...paper, the discriminating variables and the algorithms used for heavy-flavour jet identification during the first years of operation of the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, are presented. Heavy-flavour jet identification algorithms have been improved compared to those used previously at centre-of-mass energies of 7 and 8 TeV. For jets with transverse momenta in the range expected in simulated events, these new developments result in an efficiency of 68% for the correct identification of a b jet for a probability of 1% of misidentifying a light-flavour jet. The improvement in relative efficiency at this misidentification probability is about 15%, compared to previous CMS algorithms. In addition, for the first time algorithms have been developed to identify jets containing two b hadrons in Lorentz-boosted event topologies, as well as to tag c jets. The large data sample recorded in 2016 at a centre-of-mass energy of 13 TeV has also allowed the development of new methods to measure the efficiency and misidentification probability of heavy-flavour jet identification algorithms. The b jet identification efficiency is measured with a precision of a few per cent at moderate jet transverse momenta (between 30 and 300 GeV) and about 5% at the highest jet transverse momenta (between 500 and 1000 GeV).
The CMS apparatus was identified, a few years before the start of the LHC operation at CERN, to feature properties well suited to particle-flow (PF) reconstruction: a highly-segmented tracker, a ...fine-grained electromagnetic calorimeter, a hermetic hadron calorimeter, a strong magnetic field, and an excellent muon spectrometer. A fully-fledged PF reconstruction algorithm tuned to the CMS detector was therefore developed and has been consistently used in physics analyses for the first time at a hadron collider. For each collision, the comprehensive list of final-state particles identified and reconstructed by the algorithm provides a global event description that leads to unprecedented CMS performance for jet and hadronic τ decay reconstruction, missing transverse momentum determination, and electron and muon identification. This approach also allows particles from pileup interactions to be identified and enables efficient pileup mitigation methods. The data collected by CMS at a centre-of-mass energy of 8\TeV show excellent agreement with the simulation and confirm the superior PF performance at least up to an average of 20 pileup interactions.
We present a novel application of Fiber Bragg Grating (FBG) sensors in the construction and characterisation of Micro Pattern Gaseous Detector (MPGD), with particular attention to the realisation of ...the largest triple (Gas electron Multiplier) GEM chambers so far operated, the GE1/1 chambers of the CMS experiment at LHC. The GE1/1 CMS project consists of 144 GEM chambers of about 0.5 m
2
active area each, employing three GEM foils per chamber, to be installed in the forward region of the CMS endcap during the long shutdown of LHC in 2108-2019. The large active area of each GE1/1 chamber consists of GEM foils that are mechanically stretched in order to secure their flatness and the consequent uniform performance of the GE1/1 chamber across its whole active surface. So far FBGs have been used in high energy physics mainly as high precision positioning and re-positioning sensors and as low cost, easy to mount, low space consuming temperature sensors. FBGs are also commonly used for very precise strain measurements in material studies. In this work we present a novel use of FBGs as flatness and mechanical tensioning sensors applied to the wide GEM foils of the GE1/1 chambers. A network of FBG sensors have been used to determine the optimal mechanical tension applied and to characterise the mechanical tension that should be applied to the foils. We discuss the results of the test done on a full-sized GE1/1 final prototype, the studies done to fully characterise the GEM material, how this information was used to define a standard assembly procedure and possible future developments.
A
bstract
Results are presented from a search for the direct electroweak production of charginos and neutralinos in signatures with either two or more leptons (electrons or muons) of the same ...electric charge, or with three or more leptons, which can include up to two hadronically decaying tau leptons. The results are based on a sample of proton-proton collision data collected at
s
=
13
TeV, recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb
−1
. The observed event yields are consistent with the expectations based on the standard model. The results are interpreted in simplified models of supersymmetry describing various scenarios for the production and decay of charginos and neutralinos. Depending on the model parameters chosen, mass values between 180 GeV and 1150 GeV are excluded at 95% CL. These results significantly extend the parameter space probed for these particles in searches at the LHC. In addition, results are presented in a form suitable for alternative theoretical interpretations.
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