52 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
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
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
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
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
Measurements of the absolute branching fractions of B± →k±Xc c
A study of the two-body decays B±→Xc¯cK±, where Xc¯c refers to one charmonium state, is reported by the BABAR Collaboration using a data sample of 424 fb−1. The absolute determination of branching fractions for these decays are significantly improved compared to previous BABAR measurements. Evidence is found for the decay B+→X(3872)K+ at the 3σ level. The absolute branching fraction B[B+→X(3872)K+]=[2.1±0.6(stat)±0.3(syst)]×10−4 is measured for the first time. It follows that B[X(3872)→J/ψπ+π−]=(4.1±1.3)%, supporting the hypothesis of a molecular component for this resonance.publishedVersio
Light meson spectroscopy from Dalitz plot analyses of ηc decays to η0 K+K− , η0 π + π − , and ηπ + π − produced in two-photon interactions
We study the processes γγ→ηc→η′K+K−, η′π+π−, and ηπ+π− using a data sample of 519 fb−1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e− collider at center-of-mass energies at and near the Υ(nS) (n=2, 3, 4) resonances. This is the first observation of the decay ηc→η′K+K− and we measure the branching fraction Γ(ηc→η′K+K−)/(Γ(ηc→η′π+π−)=0.644±0.039stat±0.032sys. Significant interference is observed between γγ→ηc→ηπ+π− and the nonresonant two-photon process γγ→ηπ+π−. A Dalitz plot analysis is performed of ηc decays to η′K+K−, η′π+π−, and ηπ+π−. Combined with our previous analysis of ηc→K¯Kπ, we measure the K∗0(1430) parameters and the ratio between its η′K and πK couplings. The decay ηc→η′π+π− is dominated by the f0(2100) resonance, also observed in J/ψ radiative decays. A new a0(1700)→ηπ resonance is observed in the ηc→ηπ+π− channel. We also compare ηc decays to η and η′ final states in association with scalar mesons as they relate to the identification of the scalar glueball.publishedVersio
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