The Electromagnetic Calorimeter (ECAL) of the Compact Muon Solenoid (CMS) experiment at the LHC is a hermetic, fine grained, homogeneous calorimeter, containing 75,848 lead tungstate scintillating ...crystals. We highlight the key role of the ECAL in the discovery and elucidation of the Standard Model Higgs boson during LHC Run I. We discuss, with reference to specific examples from LHC Run I, the challenges of operating a crystal calorimeter at a hadron collider. Particular successes, chiefly in terms of achieving and maintaining the required detector energy resolution in the harsh radiation environment of the LHC, are described. The prospects for LHC Run II (starting in 2015) are discussed, building upon the experience gained from Run I. The high luminosity upgrade of the LHC (HL-LHC) is expected to be operational from about 2025 to 2035 and will provide instantaneous and integrated luminosities of around 5 × 1034/cm2/s and 3000/fb respectively. We outline the challenges that ECAL will face and motivate the evolution of the detector that is thought to be necessary to maintain its performance throughout LHC and High-Luminosity LHC operation.
New ε′/ ε results Biino, Cristina
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2001, Letnik:
462, Številka:
1
Journal Article
Recenzirano
Recent results on the search for direct CP violation in the neutral kaon system are discussed together with a review of the techniques used. The new preliminary result from CERN-NA48 Re(
ε′/
...ε)=(14.0±4.3)×10
−4 is presented. The current world average is Re(
ε′/
ε)=(19.3±2.4)×10
−4 establishing the existence of direct CP violation.
The kaon decays are an excellent laboratory to test low energy strong interaction perturbative theories. Recent results on radiative K
± decays from CERN NA48/2 experiment are presented. In the ...channel
K
±
→
π
±
π
0
γ
more than a million reconstructed decays have lead to the precision measurement of both the direct photon emission and inner bremsstrahlung amplitudes, with their interference term being observed for the first time. In addition the CP violating asymmetry between K
+ and K
- has been obtained to be less than
10
−
3
in this channel. We also report on the measurement of the branching fraction of the rare decay
K
±
→
π
±
γ
γ
using more than 1000 events from 20% of the full NA48/2 data set. From the spectrum of
γγ mass the decay parameter ĉ has been extracted with unprecedented precision. We measure in a model independent way the decay rate of the process
K
±
→
π
±
e
+
e
−
γ
, never observed before, using 120 events.
Since November 2009 the new Large Hadron Collider (LHC) at CERN has resumed operation delivering the first p-p collisions at 7 TeV on the 30th of March 2010. The CMS detector is registering data with ...a prospect to integrate
1
pb
−
1
of luminosity in a few months. The detector systems show excellent performances and many physics objects are already commissioned. First results on detector performance and physics, including also the 0.9 and 2.36 TeV pilot runs, are presented.
Results from recent analyses of the NA48 experiment at CERN are compared with other experiments and confronted with theoretical predictions to provide constraints on the CKM matrix and on CP ...Violation. The observable eta+- is related to the parameters of indirect and direct CPV (eta+- = epsilon + epsilon'). |eta+-| has been determined by measuring the ratio of decay rates: Gamma(K_L to pi+pi-)/Gamma(K_L to pi e nu), using an NA48 run with a dedicated pure high-intensity K_L beam. The main objective of NA48/2 has been to search for direct CP violation by high precision measurement of the asymmetry A_g = (g+ - g-)/(g+ + g-) of the linear slope parameter g in the Dalitz plot of K+- to 3pi decays. The final results from all data samples are summarised and discussed. The decay rates R(Ke3/K2pi), R(Kmu3/K2pi) and R(Kmu3/Ke3) have been measured with charged K decays from special data samples with a low bias trigger in the NA48/2 experiment. Using the latest PDG average for the (K+- to pi+- pi0) normalisation channel, the Ke3 and Kmu3 branching fractions are then used as input to deduce the CKM matrix element Vus.
After firmly establishing direct CP Violation in two pions decays of neutral kaons, the NA48 experiment at CERN-SPS has collected more than 1.6 billion of charged kaon decays into three charged ...pions, using a unique double beam technique which allows a high level of control on systematic effects.
A preliminary result is presented on the direct CP violation Dalitz plot linear slope asymmetry parameter
A
g
, that corresponds to more than an order of magnitude improvement in precision with respect to previous experiments.
The NA62 experiment, proposed to measure the very rare decay K+ to pi+ nu nubar at the CERN SPS with 10% accuracy, aims to collect about 80 events in two years of data taking, keeping background ...contamination lower than 10%. This paper describes the status of the project and the perspectives of the experiment.
PDF
