54 research outputs found
Future Experimental Improvement for the Search of LNV Process in Sector
Exploring the leptonic sector in frontier experiments is more of importance
nowadays, since the conservation of lepton flavor and total lepton number are
not guaranteed anymore in the Standard Model after the discovery of neutrino
oscillations. conversion in a
muonic atom is one of the most promising channels to investigate the lepton
number violation process, and the measurement of this process is planned in
future conversion experiments with a muonic atom in a muon-stopping
target. This paper discusses how to maximize the experimental sensitivity of
the conversion by introducing the new requirement of the mass
relation of , where is the mass of the
muon-stopping target nucleus, to get rid of the background from radiative muon
capture. The sensitivity of the conversion is anticipated to have
four orders of magnitude of improvement in forthcoming experiments using a
proper target nucleus, which satisfies the mass relation. The most promising
isotopes found are Ca and S.Comment: 8 pages, 4 figures; Figures, some numbers and a reference in text are
modifie
Track reconstruction for the COMET Phase-II experiment with ACTS
An implementation of A Common Tracking Software (ACTS) toolkit for signal
electron reconstruction for the COMET muon to electron conversion experiment is
discussed. The COMET experiment in J-PARC, Japan, will search for neutrinoless
conversion of muons into electrons in the field of an aluminium nucleus, a
lepton flavour violating process, aiming target sensitivity of . To
achieve its scientific goals, the experiment requires a reconstructed momentum
resolution of lower than 150 keV/c. For the first time by applying ACTS to
signal events in the 100 MeV energy range with multiple-turn trajectories in
the presence of background events, it is found that the reconstruction
efficiency is around 14\% with no fake reconstructed events. The implementation
details, performance, and issues of ACTS in the context of COMET are presented.Comment: 14 pages, 7 figures, Submitted to JINS
COMET Muon Conversion Experiment in J-PARC
COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of a nucleus (μ− + N → e− + N); a lepton flavor violating process. The experimental sensitivity goal for this process is order of 10−15 for Phase-I and 10−17 for Phase-II experiment, which is a factor of 100–10,000 improvements correspondingly over existing limits. Recent progresses in facility and detector development are presented, along with COMET Phase-I and Phase-II experimental schedule
GPU-Accelerated Event Reconstruction for the COMET Phase-I Experiment
This paper discusses a parallelized event reconstruction of the COMET Phase-I
experiment. The experiment aims to discover charged lepton flavor violation by
observing 104.97 MeV electrons from neutrinoless muon-to-electron conversion in
muonic atoms. The event reconstruction of electrons with multiple helix turns
is a challenging problem because hit-to-turn classification requires a high
computation cost. The introduced algorithm finds an optimal seed of position
and momentum for each turn partition by investigating the residual sum of
squares based on distance-of-closest-approach (DCA) between hits and a track
extrapolated from the seed. Hits with DCA less than a cutoff value are
classified for the turn represented by the seed. The classification performance
was optimized by tuning the cutoff value and refining the set of classified
hits. The workload was parallelized over the seeds and the hits by defining two
GPU kernels, which record track parameters extrapolated from the seeds and
finds the DCAs of hits, respectively. A reasonable efficiency and momentum
resolution was obtained for a wide momentum region which covers both signal and
background electrons. The event reconstruction results from the CPU and GPU
were identical to each other. The benchmarked GPUs had an order of magnitude of
speedup over a CPU with 16 cores while the exact speed gains varied depending
on their architectures
Study of the tau^- -> K^- pi^+ pi^- nu_tau decay
We present a study of tau^- -> K^- pi^+ pi^- nu_tau decay using ~669 /fb
data, collected with the Belle detector at the KEKB asymmetric-energy e^+ e-
collider. The data is recorded at a center-of-mass energy 10.58 GeV. The result
for the branching ratio is : B = (3.25 +- 0.02(stat.) +0.16 -0.15(sys.))x10^-3
>. We also present results of the precise measurement of the branching ratio of
other 3-prong decay modes, tau^- -> pi^- pi^+ pi^- nu_tau, tau^- -> K^- K^+
pi^- nu_tau, and tau^- -> K^- K^+ K^- nu_tau .Comment: 17 pages, 11 figures. Contributed to ICHEP08 (Philadelphia, USA, Jul.
2008) and TAU08 (Novosibirsk, Russia, Oct. 2008
Search for the Sagittarius Tidal Stream of Axion Dark Matter around 4.55 eV
We report the first search for the Sagittarius tidal stream of axion dark
matter around 4.55 eV using CAPP-12TB haloscope data acquired in March of
2022. Our result excluded the Sagittarius tidal stream of
Dine-Fischler-Srednicki-Zhitnitskii and Kim-Shifman-Vainshtein-Zakharov axion
dark matter densities of and GeV/cm,
respectively, over a mass range from 4.51 to 4.59 eV at a 90% confidence
level.Comment: 6 pages, 7 Figures, PRD Letter accepte
Extensive search for axion dark matter over 1\,GHz with CAPP's Main Axion eXperiment
We report an extensive high-sensitivity search for axion dark matter above
1\,GHz at the Center for Axion and Precision Physics Research (CAPP). The
cavity resonant search, exploiting the coupling between axions and photons,
explored the frequency (mass) range of 1.025\,GHz (4.24\,eV) to 1.185\,GHz
(4.91\,eV). We have introduced a number of innovations in this field,
demonstrating the practical approach of optimizing all the relevant parameters
of axion haloscopes, extending presently available technology. The CAPP 12\,T
magnet with an aperture of 320\,mm made of NbSn and NbTi superconductors
surrounding a 37-liter ultralight-weight copper cavity is expected to convert
DFSZ axions into approximately microwave photons per second. A powerful
dilution refrigerator, capable of keeping the core system below 40\,mK,
combined with quantum-noise limited readout electronics, achieved a total
system noise of about 200\,mK or below, which corresponds to a background of
roughly photons per second within the axion bandwidth. The
combination of all those improvements provides unprecedented search
performance, imposing the most stringent exclusion limits on axion--photon
coupling in this frequency range to date. These results also suggest an
experimental capability suitable for highly-sensitive searches for axion dark
matter above 1\,GHz.Comment: A detailed axion dark matter article with 27 pages, 22 figure
Search for rare or forbidden decays of the D0 meson
We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type D0→h'−h−ℓ'+ℓ+ and D0→h'−h+ℓ'±ℓ∓, where h and h′ represent a K or π meson and ℓ and ℓ′ an electron or muon. The analysis is based on 468 fb−1 of e+e− annihilation data collected at or close to the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the twelve modes, and we establish 90% confidence level upper limits on the branching fractions in the range (1.0–30.6)×10−7. The limits are between 1 and 3 orders of magnitude more stringent than previous measurements.publishedVersio
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