Difference between revisions of "Abstracts"
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architecture described would be easily exportable for other experiments, | architecture described would be easily exportable for other experiments, | ||
to build a versatile and fully customizable trigger system. | to build a versatile and fully customizable trigger system. | ||
| + | |||
| + | The Detector for the Kaon Rare Decays Experiment NA62 at CERN | ||
| + | |||
| + | The NA62 experiment at CERN SPS is aimed to measure ~80 events of the very rare decay K+→π+νν (BR~8.5*10-10). The experiment will use in-flight decays of 75 GeV/c positive kaons from the CERN SPS extracted proton beam. The advantages of this high energy beam are a better photon detection efficiency and an acceptance higher than for stopped kaon experiments. A disadvantage is the high /K ratio in the beam and the high particle rate (O(1 Ghz)). | ||
| + | |||
| + | The main background source comes from the decays K+→ π+ π0 and K+→For its reduction, it is foreseen to use kinematics cuts on the missing mass and hermetic photon and muon detectors. | ||
| + | With realistic π0 and muon detection inefficiencies of 10-8 and 5*10-6 respectively, the resolution on the squared missing mass should be of the order of 8*10-3. This will translate in 0.3% resolution on the kaon momentum, in better than 1% on pion momentum and of 50-60 r on the angle between the kaon and the pion. | ||
| + | This figures will be achieved with the use of the following: | ||
| + | • A beam spectrometer using achromat magnets and pixel stations (Gigatracker) able to measure the transverse coordinates of the beam in different longitudinal position to reconstruct the momentum and the direction of the parent particle. This pixel detector should stand the Gigahertz rate expected in the small beam spot size | ||
| + | • A magnetic spectrometer using a magnet with a PT kick of 270 MeV/c and a four set of straw chambers operating in the vacuum decay volume, to minimize multiple sacattering. | ||
| + | The rejection factor is degraded if the time association between the parent kaon and the pion is not good. For this the Gigatracker should also have a time resolution of better than 150 psec. | ||
| + | |||
| + | Interactions of the pion content of the beam with residual gas in the vacuum decay could mimic the signal. For this, in addition to the good quality of the vacuum (better than 10-6 mbar in the fiducial decay region), a differential Cherenkov counter (CEDAR) is located along the beamline and it will give a positive signal when a kaon is passing through it. | ||
| + | |||
| + | Photon veto counters will be placed along the vacuum decay volume, to catch large-angle photons (7 to 50 mr) with a detection efficiency better than 10-4 in a wide energy range (from few hundreds MeV to 35 GeV). In conjunction with the old NA48 LKr calorimeter and with small angle detectors at zero angle and around the beam pipe at the calorimeter level, the expected 10-8 inefficiency for π0 will be obtained. These large-angle vetoes are built using lead glass blocks from the barrel of the former OPAL electromagnetic calorimeter. | ||
| + | |||
| + | The muon rejection is accomplished with an iron-scintillator muon detector complemented with a 18-m RICH detector able to separate muons from pions above 15 GeV/c momentum. | ||
| + | |||
| + | The detector is currently under construction and the installation will be completed in spring 2012 in order to commission it for a first physics run in autumn 2012. | ||
== Abstracts 2009 == | == Abstracts 2009 == | ||
Latest revision as of 23:16, 23 March 2010
Abstracts 2010[edit]
Measurement of BR(K --> e nu)/BR(K --> mu nu)
Measurement of the helicity suppressed ratio of charged kaon leptonic decay rates BR(K --> e nu)/BR(K --> mu nu) has long been considered as an excellent test of lepton universality and the Standard Model (SM) description of weak interactions. It was realised recently that the suppression of the SM contribution might enhance the sensitivity to SUSY-induced effects to an experimentally accessible level. The NA62 experiment at the CERN SPS has collected a record number of over 105 K --> e nu decays during a dedicated run in 2007, aiming at achieving 0.5% precision. Experimental strategy, details of the analysis and preliminary results are discussed.
Measurement of the FCNC Decays K+- -> pi+- l+ l-
We report on measurements of the rare decays K+- -> pi+- e+ e- and K+- -> pi+- mu+ mu-. The full NA48/2 data set was analyzed, leading to more than 7200 reconstructed events in the electronic and more than 3000 events in the muonic channel, the latter exceeding the total existing statistics by a factor of five. For both channels the selected events are almost background-free. From these events, we have determined the branching fraction and form factors of K+- -> pi+- e+ e- using different theoretical models. Our results improve the existing world averages significantly. In addition, we measured the CP violating asymmetry between K+ and K- in this channel to be less than a few percent.
Measurement of Ks --> pipiee decay mode
The Ks to pipiee decay mode has been investigated using the data collected in 2002 by the NA48/1 collaboration. With about 23k signal events and 59k KL to pi+ pi- pi0D normalization decays, the ks to pipiee branching ratio was determined with respect to the KL one. This result is also used to set an upper limit on the presence of E1 direct emission in the decay amplitude. The CP-violating asymmetry has been also measured.
Precision Measurement of pi pi Scattering Lengths in Ke4 Decays
The measurement of the S-wave pi pi scattering lengths is a fundamental test of the validity of Chiral Perturbation Theory. We report on the final NA48/2 result, which uses the complete NA48/2 data set with more than a million reconstructed K+-e4 decays. From these events we have determined the decay form factors and pi pi scattering lengths a0_0 and a2_0. The result is the most precise measurement of the scattering lengths and in excellent agreement with the prediction of Chiral Perturbation Theory.
Precision Measurement of Photon Emission in K+- -> pi+- pi0 gamma Decays
We report our final result on the measurement of direct photon emission (DE) in the decay K+- -> pi+- pi0 gamma and its interference (INT) with the inner bremsstrahlung amplitude. For this measurement the full NA48/2 data set with about 600k reconstructed K+- -> pi+- pi0 gamma decays was analyzed, which is factor of 30 larger than for previous experiments and a factor of three w.r.t. our preliminary result. From this, the sizes of both the DE and the INT amplitudes have been measured with high precision, with the INT amplitude being observed for the first time. In addition, the CP violating asymmetry between K+ and K- has been obtained to be less than 103 in this channel.
Measurement of the rare Decay K+- -> pi+- gamma gamma
We report on the measurement of the branching fraction of the rare decay K+- -> pi+- gamma gamma using the full NA48/2 dataset of more than 5000 reconstructed decays from the full NA48/2 data set. From the spectrum of the invariant gamma gamma mass, the decay parameter c^ can be extracted with unprecedented precision.
Measurement of the radiative Decay K+- -> pi0 e+- nu_e gamma (Ke3gamma)
We report on the measurement of more than 200000 events of the decay K+- -> pi0 e+- nu_e gamma, recorded with the NA48/2 detector at CERN. These statistics, about two orders of magnitude more than previous experiments, allow measurements of the decay rate and of possible CP violation in this decay with per cent precision.
The NA62 RICH detector
The CERN NA62 experiment aims at a 10% measurement of the BR of the K+ into a pi+ and two neutrinos. The main background is the K+ decay into a muon and a neutrino, so pion-muon separation is a crucial ingredient. The RICH detector must separate pions from muons at 3 sigma level between 15 and 35 GeV/c momentum. The RICH must also measure the pion crossing time with a 100 ps resolution to avoid fake coincidences with an upstream beam spectrometer. To fufill these requirements a RICH filled with Neon at atmospheric pressure has been chosen, with a radiator length of 17 m. A mosaic of 20 hexagonal or semi-hexagonal mirrors with 17 m focal length, placed at the downstream end of the detector, will reflect the Cherenkov light onto two spots (to avoid the shadow induced by a beam pipe crossing the detector) located at the upstream end of the RICH where 2000 photomultipliers in total will be placed. Single anode photomultipliers, put at 18 mm minimum distance among each other have been chosen to match the required time resolution and Cherenkov angle sensitivity. A prototype was built to validate the project, with the same longitudinal dimensions (17 m) but reduced transverse size with respect to the final detector. In 2007 the prototype, equipped with 96 photomultipliers and exposed to a pion beam at CERN, showed a time resolution smaller than 100 ps. In 2009 in another test beam the prototype was equipped with 414 photomultipliers and demonstrated the capability to suppress by a factor 100 the muon background with respect to charged pions in a 15-35 GeV/c momentum range. The detector, approved and fully financed, is now in its construction phase with commissioning foreseen in 2012. The details of the project and the results of the test beams will be discussed.
GPU for RT2010
We describe a pilot project for the use of GPUs (Graphics processing unit) in an on-line triggering application at the CERN NA62 experiment.
Recently the interest in using GPUs for general purpose application is growing due to the high performances achieved: the present generation of chips allows a peak computing performance of about 1 Teraflops and the next incoming generation will deliver around a factor of two more.
In high energy physics experiments the on-line selection is a fundamental part of the Data acquisition system, in order to reduce the bandwidth requirements and the total amount of data that have to be recorded on tape. The standard trigger systems are structured in several levels realized in custom hardware and software.
The computing power of the GPUs allows to imagine a real-time system in which trigger decision are taken directly in the video processor with a stable latency. This could greatly simplify the standard solutions adopted for triggering, usually based on custom FPGA or ASIC.
The ongoing work presented here shows the results achieved in pattern matching problems to define trigger primitives, in particular related to particle identification in the RICH detector of the NA62 experiment, where the rate of events to be analyzed will be around 10 MHz. The results obtained in simulation and lab tests are very encouraging to go towards a working prototype.
Due to the use of off-the-shelf technology, in continuous development for other purposes (Video Games, image editing,...), the architecture described would be easily exportable for other experiments, to build a versatile and fully customizable trigger system.
The Detector for the Kaon Rare Decays Experiment NA62 at CERN
The NA62 experiment at CERN SPS is aimed to measure ~80 events of the very rare decay K+→π+νν (BR~8.5*10-10). The experiment will use in-flight decays of 75 GeV/c positive kaons from the CERN SPS extracted proton beam. The advantages of this high energy beam are a better photon detection efficiency and an acceptance higher than for stopped kaon experiments. A disadvantage is the high /K ratio in the beam and the high particle rate (O(1 Ghz)).
The main background source comes from the decays K+→ π+ π0 and K+→For its reduction, it is foreseen to use kinematics cuts on the missing mass and hermetic photon and muon detectors. With realistic π0 and muon detection inefficiencies of 10-8 and 5*10-6 respectively, the resolution on the squared missing mass should be of the order of 8*10-3. This will translate in 0.3% resolution on the kaon momentum, in better than 1% on pion momentum and of 50-60 r on the angle between the kaon and the pion. This figures will be achieved with the use of the following: • A beam spectrometer using achromat magnets and pixel stations (Gigatracker) able to measure the transverse coordinates of the beam in different longitudinal position to reconstruct the momentum and the direction of the parent particle. This pixel detector should stand the Gigahertz rate expected in the small beam spot size • A magnetic spectrometer using a magnet with a PT kick of 270 MeV/c and a four set of straw chambers operating in the vacuum decay volume, to minimize multiple sacattering. The rejection factor is degraded if the time association between the parent kaon and the pion is not good. For this the Gigatracker should also have a time resolution of better than 150 psec.
Interactions of the pion content of the beam with residual gas in the vacuum decay could mimic the signal. For this, in addition to the good quality of the vacuum (better than 10-6 mbar in the fiducial decay region), a differential Cherenkov counter (CEDAR) is located along the beamline and it will give a positive signal when a kaon is passing through it.
Photon veto counters will be placed along the vacuum decay volume, to catch large-angle photons (7 to 50 mr) with a detection efficiency better than 10-4 in a wide energy range (from few hundreds MeV to 35 GeV). In conjunction with the old NA48 LKr calorimeter and with small angle detectors at zero angle and around the beam pipe at the calorimeter level, the expected 10-8 inefficiency for π0 will be obtained. These large-angle vetoes are built using lead glass blocks from the barrel of the former OPAL electromagnetic calorimeter.
The muon rejection is accomplished with an iron-scintillator muon detector complemented with a 18-m RICH detector able to separate muons from pions above 15 GeV/c momentum.
The detector is currently under construction and the installation will be completed in spring 2012 in order to commission it for a first physics run in autumn 2012.
Abstracts 2009[edit]
Excited QCD
Tests of Chiral Perturbation Theory with Ke4 decays at NA48
Precision measurement of photon emission in K+- -> pi+- pi0 gamma decays
Moriond QCD
Precision measurement of photon emission in K+- -> pi+- pi0 gamma decays
Measurement of the FCNC decays K+- -> pi+- l+ l-
TIPP09
The Trigger System for the NA62 experiment at the CERN SPS
The Photon Veto System for the NA62 Rare Kaon Decay Experiment
Pixel Read-Out Architectures for the NA62 Gigatracker
Usage of Silicon PhotoMultipliers for the CEDAR ...
Animma
The Trigger System for the NA62 experiment at the CERN SPS
The Photon Veto System for the NA62 Rare Kaon Decay Experiment
Pixel Read-Out Architectures for the NA62 Gigatracker
Usage of Silicon PhotoMultipliers for the CEDAR ...
GHP2009
CIPANP
Search of New Physics with Kaon decays at NA62
Blois
Search of New Physics with Kaon decays at NA62
PASCOS2009
Search of New Physics with Kaon decays at NA62
Lomonosov
