120443217
Low mass dimuon production in proton-nucleus collisions at 400-GeV/c
The NA60 experiment has studied low-mass muon pair production in proton-nucleus collisions with a system of Be, Cu, In, W, Pb and U targets using a 400 GeV/c proton beam at the CERN SPS. The mass spectrum is well described by the superposition of the two-body and Dalitz decays of the light neutral mesons η, ρ, ω, η′ and ϕ new measurement of the electromagnetic transition form factors of the η and ω was performed. The values found are Λη−2=1.950±0.059(stat.)±0.042(syst.)(GeV/c2)−2 and Λω−2=2.241±0.025(stat.)±0.028(syst.)(GeV/c2)−2. They agree with the previous available measurements, improving their uncertainty thanks to the higher statistics, and confirm the discrepancy with the prediction of the Vector Meson Dominance model in the case of the electromagnetic form factor of the ω meson. The comparison of the data to an improved calculation including also a direct point-like term is discussed. The nuclear dependence of the production cross sections of the ω, ρ and ϕ mesons was also studied. An increase of the ϕ production with respect to the ω is observed from p-Be to p-U collisions. Parameterizing the nuclear dependence of the production cross sections with the power law σpA∝Aα, one finds αω=0.841±0.014(stat.)±0.030(syst.) and αϕ=0.906±0.011(stat.)±0.025(syst.). A possible bias induced by the use of the light Be target is found. If it is excluded, the results are αω=0.801±0.037(stat.)±0.041(syst.) and αϕ=0.963±0.026(stat.)±0.017(syst.), showing an increase of αϕ and a decrease of αω.
196068018
NA60 Status Report
125411098
Radiation studies for the Readout Electronic of the ALICE Dimuon Forward Spectrometer
120201082
Radiation damage effects in the NA60 silicon pixel detectors
Abstract The NA60 experiment studies open charm and prompt dimuon production in proton–nucleus and nucleus–nucleus collisions at the CERN SPS. Downstream of the target system a silicon pixel telescope made with p-on-n silicon sensors measures the charged tracks originating from the collisions. During the 2003 data taking period with indium–indium collisions a significant radiation dose was collected. Simulations done before the run predicted a fluence of up to several 10 13 1 MeV n eq cm - 2 in the most affected regions of the sensors and a difference of approximately a factor ten between the inner and outer regions of certain sensor chips. The inhomogeneous distribution of the fluence leads to type inversion in some regions of the sensors while other regions of the same sensors kept their initial behaviour. The depletion voltages and leakage currents were measured during the run and have been compared with the estimates we had previously made. This paper shows simulation results of fluence and radiation damage and comparisons with the measurements performed throughout the data taking period.
120473193
Trigger of low pT muons with the ATLAS hadronic calorimeter
Abstract A strategy for tagging muons with the Tile Calorimeter at the second level trigger (LVL2) of the ATLAS experiment is presented and its efficiency and mistagging fraction are discussed. It is demonstrated that the Tile Calorimeter can identify muons with good efficiency down to p T =2 GeV /c where the stand-alone muon spectrometer has zero efficiency. A method of exploiting all information available at LVL2 to reduce spurious muon-tag and measure the candidate muon momentum is discussed. The effectiveness of this method is tested, in particular, in the case of b b events at low Large Hadron Collider luminosity (10 33 cm −1 s −2 ) with full simulation of experimental conditions.
53139097
Implementation and performance of the ATLAS trigger muon "vertical slice"
The ATLAS (A Toroidal LHC ApparatuS) trigger system is designed to keep high effiency for interesting events while achieving a rejection of low transverse momentum ( p T ) physics of about 10 7 , thus reaching the ∼200 Hz data storage capability of the Data Aquisition system. A three levels structure has been implemented for this purpose, as described in this work for the case of the muon trigger system. After describing the implementation, some performance results are presented in terms of final trigger rates, resolutions, efficiencies, background rejection and algorithm latency.
53052258
Signal Reconstruction of the ATLAS Hadronic Tile Calorimeter: implementation and performance
TileCal, the central hadronic section of the ATLAS Calorimeter, is a sampling calorimeter made of steel and scintillating tiles. The TileCal front-end electronics reads out about 10,000 photo-multipliers at 40 Msps measuring energies ranging from 30 MeV to 2 TeV. The read-out system is designed to provide the ATLAS High Level Trigger with reconstructed PMT signals within the time budget allowed by the First Level Trigger (LVL1) running at a maximum trigger rate of 75 KHz. The signal amplitude, time and a reconstruction quality factor are obtained for each PMT using optimal filtering techniques implemented in the Digital Signal Processors (DSP).
198461351
Muons in the calorimeters: Energy loss corrections and muon tagging
112985462
Electromagnetic Compatibility of a Low Voltage Power Supply for the ATLAS Tile Calorimeter Front-End Electronics
The front-end electronics of the ATLAS Tile Calorimeter is powered by DC/DC converters that sit close to it. The performance of the detector electronics is constrained by the conducted noise emissions of its power supply. A compatibility limit is defined for the system. The noise susceptibility of the front-end electronics is evaluated, and different solutions to reduce the front-end electronics noise are discussed and tested. I. POWER DISTRIBUTION SCHEME FOR THE TILE CALORIMETER The front-end electronics of the Tile Calorimeter [1] is organized in drawers that are inserted in detector modules. Each drawer is 3 meter long and contains the front-end analogue and digitizing electronics for 45 photomultiplier tubes [2] in the case of the barrel modules. It is powered by eight regulated low voltage lines, and it is rated to consume a maximum power of 300W. Because a drawer requires a tight voltage regulation on its power lines, the low voltage power supply was designed to fit in its vicinity, as an extension of it. The environmental constrains such as radiation and magnetic field tolerance were solved with the design of custom DC/DC converters that are remotely controlled by an ELMB [3]. The power supply is located in a closed volume known as finger. The power supply is water cooled. Figure 1: Finger low voltage power supply of the ATLAS Tile Calorimeter. The finger low voltage power supplies (figure 1) are fed by bulk power supplies (200VDC) located in a control room. Auxiliary power supplies in the same control room are also required to power separately the monitoring and control circuitry. The power system (figure 2) is controlled by the Detector Control System (DCS) through a CANBus line that communicates with the ELMB of the power supply. The low voltage outputs are isolated from earth, but all the return lines are put in common inside the drawer. Figure 2: Tile Calorimeter power distribution scheme. NOISE PERFORMANCE TEST METHODS The front-end noise is composed by the drawer electronics noise, by the power supply noise and by the external couplings on the interconnecting cables (not studied here). A. System Noise. The achievable performance of the drawer electronics in terms of noise is limited by design. The system noise in each front-end channel was measured in detail on drawers that were powered with low noise linear power supplies. The system noise is evaluated in terms of high frequency and low frequency contributions from the data taken with the full data acquisition chain. The high frequency noise seen by the fast readout electronics is estimated from the pedestals data. The estimation is based on a selection of parameters computed over several runs and on all the channels of a drawer: • RMS of the pedestals distribution. • Gaussian property of the pedestals distribution. Module DRAWER LVPS Finger 200VDC