19 research outputs found
Pinning down the kaon form factors in K^+ -> mu^+ nu_mu gamma decay
We find that the normal muon polarization in the decay K->mu nu_mu gamma is
very sensitive to the values of the kaon vector F_V and axial-vector F_A form
factors. It is shown that the ongoing KEK-E246 experiment can definitely
determine the signs of the sum of the form factors if their difference is fixed
from other considerations. This method can also verify the form factor values
and signs obtained from the K^+ -> l^+ nu_l e^+ e^- decays. A new experiment
with sensitivity to the normal and transverse muon polarizations of about 10^-4
will provide a unique possibility to determine the F_V and F_A values with a
few percent accuracy.Comment: revtex, 5 pages, 2 figures. Minor corrections made for the journal
version of the pape
T-Odd Correlations in pi->e nu_e gamma and pi->mu nu_mu gamma Decays
The transverse lepton polarization asymmetry in pi_l2gamma decays may probe
T-violating interactions beyond the Standard Model. Dalitz plot distributions
of the expected effects are presented and compared to the contribution from the
Standard Model final state interactions. We give an example of a
phenomenologically viable model, where a considerable contribution to the
transverse lepton polarization asymmetry arises.Comment: 19 pages, 5 figures. To be published in Phys.Rev.D. Fixed sign in FSI
contribution figure, fixed formulas in K-bar{K} mixing analysis, added some
minor comment
Measurement of K^+ \to \pi^0 \mu^+ \nu \gamma decay using stopped kaons
The K^+ \to \pi^0 \mu^+ \nu \gamma () decay has been
measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A
sample containing 125 events was obtained. The partial
branching ratio was found to be , which is in good agreement with theoretical predictions.Comment: 12 pages, 3 figures, to be published in Physics Letters
Measurement of direct photon emission in decay using stopped positive kaons
The radiative decay () has
been measured with stopped positive kaons. A sample
containing 4k events was analyzed, and the branching ratio
of the direct photon emission process was determined to be . No interference pattern with internal
bremsstrahlung was observed.Comment: 12 pages, 6 figures, 2 tables, to be published in Phys. Lett.
Apparatus for a Search for T-violating Muon Polarization in Stopped-Kaon Decays
The detector built at KEK to search for T-violating transverse muon
polarization in K+ --> pi0 mu+ nu (Kmu3) decay of stopped kaons is described.
Sensitivity to the transverse polarization component is obtained from
reconstruction of the decay plane by tracking the mu+ through a toroidal
spectrometer and detecting the pi0 in a segmented CsI(Tl) photon calorimeter.
The muon polarization was obtained from the decay positron asymmetry of muons
stopped in a polarimeter. The detector included features which minimized
systematic errors while maintaining high acceptance.Comment: 56 pages, 30 figures, submitted to NI
T-odd correlation in the K+ ->pi l nu gamma decays beyond Standard Model
The dependence of the T-odd correlation on the effective Lagrangian
parameters in the decays is analyzed. It
is shown that the introduced observable is perspective in a search for new
physics in the vector and pseudovector sector of the Lagrangian. As for scalar
and pseudoscalar sectors, the T-odd correlation studies will not allow one to
improve current restrictions on parameters of models beyond SM.Comment: 18 pages, 1 figur
Measurement of ratio using stopped positive kaons
The ratio of the () and () decay widths, , has been measured with stopped positive kaons.
and samples containing 2.4 and 4.0 events, respectively, were analyzed. The
ratio was obtained to be
0.6710.007(stat.)0.008(syst.) calculating the detector acceptance by
a Monte Carlo simulation with the assumption of - universality in
decay. The coefficient of the dependent term of the form
factor was also determined to be
=0.0220.005(stat.)0.004(syst.).Comment: 12 pages, 6 figure
Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target
The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About 1011 muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to (3.27±0.07) à 1011 protons on target was recorded. This amounts to approximatively 1% of a SHiP spill
Track reconstruction and matching between emulsion and silicon pixel detectors for the SHiP-charm experiment
In July 2018 an optimization run for the proposed charm cross section measurement for SHiP was performed at the CERN SPS. A heavy, moving target instrumented with nuclear emulsion films followed by a silicon pixel tracker was installed in front of the Goliath magnet at the H4 proton beam-line. Behind the magnet, scintillating-fibre, drift-tube and RPC detectors were placed. The purpose of this run was to validate the measurement's feasibility, to develop the required analysis tools and fine-tune the detector layout. In this paper, we present the track reconstruction in the pixel tracker and the track matching with the moving emulsion detector. The pixel detector performed as expected and it is shown that, after proper alignment, a vertex matching rate of 87% is achieved
Development of electronics and data acquisition system for the J-PARC T59 (WAGASCI) experiment
International audienceWAGASCI is a new experiment at J-PARC neutrino beamline, to measure the cross section ratio of charged current neutrino interaction on nucleus between water target and plastic target with the accuracy of a few percent. The detector adopts three-dimensional grid structure of 3-mm- thick scintillator bars around water and plastic targets, to obtain large angular acceptance. As a photodetector a 32-channel arrayed MPPC has been developed for the WAGASCI detector. The WAGASCI detector has 1280 MPPC channels in total. Our front-end electronics is SPIROC2D, which is an auto-triggered, bi-gain, 36-channel ASIC, allowing to measure the charge from one to 2000 photoelectron and the time with 100ps step. It contains a 16-deep analog memory array, which allows to store 16 hits in an acquisition gate. The back-end boards control the data output from the front-end ASIC and reception of trigger signals for neutrino beam. The module con- struction has been completed and the data acquisition system has almost been completed, to be ready for the neutrino beam measurement from October 2017