arXiv subjects

P. Kitching

Publications and source records attributed to P. Kitching.

13 recordsLinked to original sources

arXiv2016

Measurement of $\sigma_{\mathrm{ABS}}$ and $\sigma_{\mathrm{CX}}$ of $\pi^+$ on carbon by DUET

The DUET Collaboration reports on the measurements of the absorption ($\sigma_{\mathrm{ABS}}$) and charge exchange ($\sigma_{\mathrm{CX}}$) cross sections of positively charged pions on carbon nuclei for the momentum range 201.6 MeV$/c$ to 295.1 MeV$/c$. The uncertainties on the absorption and charge exchange cross sections are $\sim$9.5\% and $\sim$18\%, respectively. The results are in good agreement with previous experiments. A covariance matrix correlating the 5 $\sigma_{\mathrm{ABS}}$ and 5 $\sigma_{\mathrm{CX}}$ measured data points is also reported

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arXiv2016

Search for the rare decay $K^+\to\mu^+\nu\bar\nu\nu$

Evidence of the $K^+\to\mu^+\nu\bar\nu\nu$ decay was searched for using E949 experimental data with an exposure of $1.70\times 10^{12}$ stopped kaons. The data sample is dominated by the backgrond process $K^+\to\mu^+\nu_\mu\gamma$. An upper limit on the decay rate $\Gamma(K^+\to\mu^+\nu\bar\nu\nu)< 2.4\times 10^{-6}\Gamma(K^+\to all)$ at 90% confidence level was set assuming the Standard Model muon spectrum. The data are presented in such a way as to allow calculation of rates for any assumed $\mu^+$ spectrum.

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arXiv2015

Measurement of absorption and charge exchange of $\pi^+$ on carbon

The combined cross section for absorption and charge exchange interactions of positively charged pions with carbon nuclei for the momentum range 200 MeV/c to 300 MeV/c have been measured with the DUET experiment at TRIUMF. The uncertainty is reduced by nearly half compared to previous experiments. This result will be a valuable input to existing models to constrain pion interactions with nuclei.

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arXiv2014

Search for heavy neutrinos in $K^+\to\mu^+\nu_H$ decays

Evidence of a heavy neutrino, $\nu_H$, in the $K^+\to\mu^+\nu_H$ decays was sought using the E949 experimental data with an exposure of $1.70\times 10^{12}$ stopped kaons. With the major background from the radiative $K^+\to\mu^+\nu_\mu\gamma$ decay understood and suppressed, upper limits (90% C.L.) on the neutrino mixing matrix element between muon and heavy neutrino, $|U_{\mu H}|^2$, were set at the level of $10^{-7}$ to $10^{-9}$ for the heavy neutrino mass region 175 to 300 MeV/$c^2$.

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arXiv2009

Study of the decay K+ => pi+,nu,nubar in the momentum region 140<Ppi<199 MeV/c

Experiment E949 at Brookhaven National Laboratory has observed three new events consistent with the decay K+ => pi+,nu,nubar in the pion momentum region 140 < P_pi < 199 MeV/c in an exposure of 1.71e12 stopped kaons with an estimated total background of 0.93+-0.17(stat.)+0.32-0.24(syst.) events. This brings the total number of observed K+ => pi+,nu,nubar events to seven. Combining this observation with previous results, assuming the pion spectrum predicted by the standard model, results in a branching ratio of (1.73+1.15-1.05)e-10. An interpretation of the results for alternative models of the decay K^ => pi+,nothing is also presented.

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arXiv2008

A Precision Measurement of the Muon Decay Parameters $ρ$ and $δ$

The TWIST collaboration has performed new measurements of two of the parameters that describe muon decay: $ρ$, which governs the shape of the overall momentum spectrum, and $δ$, which governs the momentum dependence of the parity-violating decay asymmetry. This analysis gives the results $ρ=0.75014\pm 0.00017(\text{stat})\pm 0.00044(\text{syst})\pm 0.00011(η)$, where the last uncertainty arises from the correlation between $ρ$ and the decay parameter $η$, and $δ= 0.75067\pm 0.00030(\text{stat})\pm 0.00067(\text{syst})$. These are consistent with the value of 3/4 given for both parameters in the Standard Model of particle physics, and are a factor of two more precise than the measurements previously published by TWIST. A new global analysis of all available muon decay data incorporating these results is presented. Improved lower and upper limits on the decay parameter $P_μ^πξ$ of $0.99524 < P_μ^πξ\leq ξ< 1.00091$ at 90% confidence are determined, where $P_μ^π$ is the polarization of the muon when it is created during pion decay, and $ξ$ governs the muon decay asymmetry. These results set new model-independent constraints on the possible weak interactions of right-handed particles. Specific implications for left-right symmetric models are discussed.

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arXiv2006

Measurement of P_{mu}xi in Polarized Muon Decay

The quantity P_{mu}^{pi}xi, where xi is one of the muon decay parameters and $P_{\mu}^{\pi}$ is the degree of muon polarization in pion decay, has been measured. The value P_{mu}^{pi}xi = 1.0003 +- 0.0006 stat. +- 0.0038 syst. was obtained. This result agrees with previous measurements but is over a factor of two more precise. It also agrees with the Standard Model prediction for P_{mu}^{pi}xi and thus leads to restrictions on left-right symmetric models.

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arXiv2004

Measurement of the Muon Decay Parameter delta

The muon decay parameter delta has been measured by the TWIST collaboration. We find delta = 0.74964 +- 0.00066(stat.) +- 0.00112(syst.), consistent with the Standard Model value of 3/4. This result implies that the product Pmuxi of the muon polarization in pion decay, Pmu, and the muon decay parameter xi falls within the 90% confidence interval 0.9960 < Pmuxi < xi < 1.0040. It also has implications for left-right-symmetric and other extensions of the Standard Model.

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arXiv2000

Search for the Decay K+ -> pi+ pi0 nu nubar

The first search for the decay K^+ -> pi^+ pi^0 nu nubar has been performed with the E787 detector at BNL. Based on zero events observed in the kinematical search region defined by 90 MeV/c < P_{pi^+} < 188 MeV/c and 135 MeV < E_{pi^0} < 180 MeV, an upper limit B(K^+ -> pi^+ pi^0 nu nubar) < 4.3 x 10^{-5} at 90% confidence level is established.

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arXiv1998

Upper Limit on the Decay K+ --> e+ nu mu+ mu-

An upper limit on the branching ratio for the decay K+ --> e+ nu mu+ mu- is set at 5.0 x 10^{-7} at 90% confidence level, consistent with predictions from chiral perturbation theory.

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arXiv1997

Observation of the Decay K^+ --> pi^+ gamma gamma

The first observation of the decay K^+ --> pi^+ gamma gamma is reported. A total of 31 events was observed with an estimated background of 5.1 +- 3.3 events in the pi+ momentum range from 100 MeV/c to 180 MeV/c. The corresponding partial branching ratio, B(K+ -> pi+ gamma gamma, 100 MeV/c < P_pi^+ < 180 MeV/c), is (6.0 +- 1.5 (stat) +- 0.7 (sys)) x 10^{-7}. No K^+ --> pi^+ gamma gamma decay was observed in the pi^+ momentum region greater than 215 MeV/c. The observed pi^+ momentum spectrum is compared with the predictions of chiral perturbation theory.

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arXiv1997

Observation of the Decay K+ --> pi+ mu+ mu-

We have observed the rare decay K+ --> pi+ mu+ mu- and measured the branching ratio Gamma(K+ --> pi+ mu+ mu-)/Gamma(K+ --> all) = (5.0 +/- 0.4 (stat.) +/- 0.7 (sys.) +/- 0.6 (theor.)) x 10^{-8}. We compare this result with predictions from chiral perturbation theory and estimates based on the decay K+ --> pi+ e+ e-.

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arXiv1995

Search for the Decay $K^+ \to π^+ ν\overlineν$

An upper limit on the branching ratio for the decay $K^+ \! \rightarrow \! π^+ ν\overlineν$ is set at $2.4 \times 10^{-9}$ at the 90\% C.L. using pions in the kinematic region $214~{\rm MeV}/c < P_π< 231~{\rm MeV}/c$. An upper limit of $5.2 \times 10^{-10}$ is found on the branching ratio for decays $K^+ \! \rightarrow \! π^+ X^0$, where $X^0$ is any massless, weakly interacting neutral particle. Limits are also set for cases where $M_{X^0}>0$.

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