Search for heavy neutrinos in K + → μ + ν H decays Artamonov, A. V.; Bassalleck, B.; Bhuyan, B. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
03/2015, Letnik:
91, Številka:
5
Journal Article
Odprti dostop
Here, evidence of a heavy neutrino, νH, in the K+→μ+νH decays was sought using the E949 experimental data with an exposure of 1.70 × 1012 stopped kaons. With the major background from the radiative ...K+→μ+νμγ decay understood and suppressed, upper limits (90% C.L.) on the neutrino mixing matrix element between the muon and heavy neutrinos, |UμH|2, were set at the level of 10–7 to 10–9 for the heavy neutrino mass region 175 to 300 MeV/c2.
Interbunch extinction measurement at the BNL AGS for the KOPIO experiment Ahrens, L.; Artamonov, A.; Atoian, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2006, Letnik:
560, Številka:
2
Journal Article
Recenzirano
The KOPIO experiment at the BNL AGS required an extracted proton beam in which a debunched, coasting beam is forced between empty longitudinal RF buckets to form microbunches. The goal of the ...measurement described here was to obtain a low background determination of the fraction of protons coming from the AGS slowly extracted beam at times between microbunches (interbunch extinction). The effect on interbunch extinction of variations in the RF cavity voltage, the momentum dispersion of the beam and the main guide field voltage-ripple was studied. It was found that there exists a broad range of operating parameters that could allow the AGS to produce microbunches with the interbunch extinction better than the KOPIO experiment requirement. Results obtained in this study gave interbunch extinctions better than 10
−5 (1%) of KOPIO's upper limit.
We report on a plan to establish a ‘Dictionary of LHC Signatures’, an initiative that started at the WHEPP-X workshop in Chennai, January 2008. This study aims at the strategy of distinguishing 3 ...classes of dark matter motivated scenarios such as
R
-parity conserved supersymmetry, little Higgs models with
T
-parity conservation and universal extra dimensions with KK-parity for generic cases of their realization in a wide range of the model space. Discriminating signatures are tabulated and will need a further detailed analysis.
We have searched for the K{sup +} {yields} {pi}{sup +}{gamma}{gamma} decay in the kinematic region with {pi}{sup +} momentum close to the end point. No events were observed, and the 90% ...confidence-level upper limit on the partial branching ratio was obtained, B(K{sup +} {yields} {pi}{sup +}{gamma}{gamma}, P > 213 MeV/c) < 8.3 x 10{sup -9} under the assumption of chiral perturbation theory including next-to-leading order ''unitarity'' corrections. The same data were used to determine an upper limit on the K{sup +} {yields} {pi}{sup +}{gamma} branching ratio of 2.3 x 10{sup -9} at the 90% confidence level.
Three events for the decay K+-->pi+ nunu have been observed in the pion momentum region below the K+-->pi+pi0 peak, 140 < Ppi < 199 MeV/c, with an estimated background of 0.93+/-0.17(stat.) ...-0.24+0.32(syst.) events. Combining this observation with previously reported results yields a branching ratio of B(K+-->pi+ nunu) = (1.73(-1.05)+1.15) x 10(-10) consistent with the standard model prediction.
The ATLAS Inner Detector (ID) trigger algorithms ran online during data taking with proton-proton collisions at the Large Hadron Collider (LHC) in December 2009. Preliminary results on the ...performance of the algorithms in collisions at centre-of-mass energy of 900 GeV are presented, including comparisons to the ATLAS offline tracking algorithms and to simulations. The ATLAS trigger performs the online event selection in three stages. The ID information is used in the second and third triggering stages, called Level-2 trigger (L2) and Event Filter (EF) respectively, and collectively the High Level Triggers (HLT). The HLT runs software algorithms in a large farm of commercial CPUs and is designed to reject collision events in real time, keeping the most interesting few in every thousand. The average execution time per event at L2(EF) is about 40 ms(4s) and the ID trigger algorithms can take only a fraction of that. Within this time, the data from interesting regions of the ID have to be accessed from central buffers through the network, unpacked, clustered and converted to the ATLAS global coordinates, then pattern recognition follows to identify the trajectories of charged particles (tracks), and finally these tracks are used in combination with other information to accept or reject events, according to whether they satisfy one or more trigger signatures. The various clients of the ID trigger information impose different constraints in the performance of the pattern recognition, in terms of efficiency and fake rate for tracks. An overview of the different uses of the ID trigger algorithms is given, and their online performance is exemplified with results from the use of L2 tracks for the online determination of the LHC beam position.
We have searched for the K+→π+γγ decay in the kinematic region with π+ momentum close to the end point. No events were observed, and the 90% confidence-level upper limit on the partial branching ...ratio was obtained, B(K+→π+γγ,P>213 MeV/c)<8.3×10−9 under the assumption of chiral perturbation theory including next-to-leading order “unitarity” corrections. The same data were used to determine an upper limit on the K+→π+γ branching ratio of 2.3×10−9 at the 90% confidence level.
An additional event near the upper kinematic limit for K+-->pi(+)nunu; has been observed by experiment E949 at Brookhaven National Laboratory. Combining previously reported and new data, the ...branching ratio is B(K+-->pi(+)nunu;)=(1.47(+1.30)(-0.89))x10(-10) based on three events observed in the pion momentum region 211<P<229 MeV/c. At the measured central value of the branching ratio, the additional event had a signal-to-background ratio of 0.9.
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