arXiv subjects

J. M. Link

Publications and source records attributed to J. M. Link.

At least 91 records · Page 5Linked to original sources

arXiv2005

Study of the decay asymmetry parameter and CP violation parameter in the Lambdac+ --> Lambda pi+ decay

Using data from the FOCUS (E831) experiment at Fermilab, we present a new measurement of the weak decay-asymmetry parameter alpha(Lambdac) in Lambdac --> Lambda pi decay. Comparing particle with antiparticle decays, we obtain the first measurement of the CP violation parameter : A = [alpha(Lambdac)+alpha(antiLambda_c)]/[alpha(Lambdac)-alpha(antiLambda_c)]. We obtain alpha(Lambdac)=-0.78+-0.16+-0.13 and A = -0.07+-0.19+-0.12 where errors are statistical and systematic.

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arXiv2005

Search for $Λ_c^+ \to p K^+ π^-$ and $D_s^+ \to K^+ K^+ π^-$ Using Genetic Programming Event Selection

We apply a genetic programming technique to search for the double Cabibbo suppressed decays $Λ_c^+ \to p K^+ π^-$ and $D_s^+ \to K^+ K^+ π^-$. We normalize these decays to their Cabibbo favored partners and find $\text{BR}($Λ_c^+ \to p K^+ π^-$)/\text{BR}($Λ_c^+ \to p K^- π^+$) = (0.05 \pm 0.26 \pm 0.02)%$ and $\text{BR}($D_s^+ \to K^+ K^+ π^-$)/\text{BR}($D_s^+ \to K^+ K^- π^+$) = (0.52\pm 0.17\pm 0.11)%$ where the first errors are statistical and the second are systematic. Expressed as 90% confidence levels (CL), we find $< 0.46 % $ and $ < 0.78%$ respectively. This is the first successful use of genetic programming in a high energy physics data analysis.

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arXiv2005

A Measurement of the Ds+ Lifetime

A high statistics measurement of the Ds+ lifetime from the Fermilab fixed-target FOCUS photoproduction experiment is presented. We describe the analysis of the two decay modes, Ds+ -> phi(1020)pi+ and Ds+ -> \bar{K}*(892)0K+, used for the measurement. The measured lifetime is 507.4 +/- 5.5 (stat.) +/- 5.1 (syst.) fs using 8961 +/- 105 Ds+ -> phi(1020)pi+ and 4680 +/- 90 Ds+ -> \bar{K}*(892)0K+ decays. This is a significant improvement over the present world average.

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arXiv2005

Application of Genetic Programming to High Energy Physics Event Selection

We review genetic programming principles, their application to FOCUS data samples, and use the method to study the doubly Cabibbo suppressed decay D+ -> K+ pi+ pi- relative to its Cabibbo favored counterpart, D+ -> K- pi+ pi+. We find that this technique is able to improve upon more traditional analysis methods. To our knowledge, this is the first application of the genetic programming technique to High Energy Physics data.

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arXiv2005

Measurement of the doubly Cabibbo suppressed decay $D^0 \to K^+π^-$ and a search for charm mixing

We present an analysis of the decay $D^0 \to K^+π^-$ based on FOCUS data. From a sample of 234 signal events, we find a branching ratio of $\frac{Γ(D^0 \to K^+π^-)}{Γ(D^0 \to K^-π^+)} = (0.429^{+0.063}_{-0.061}\pm 0.027)%$ under the assumptions of no mixing and no CP violation. Allowing for CP violation, we find a branching ratio of $(0.429 \pm 0.063 \pm 0.028)%$ and a \textit{CP} asymmetry of $0.18 \pm 0.14 \pm 0.04$. The branching ratio for the case of mixing with no CP violation is $(0.381^{+0.167}_{-0.163} \pm 0.092)%$. We also present limits on charm mixing.

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arXiv2004

Analysis of the semileptonic decay $D^0 \to \bar{K}^0 π^-μ^+ν$

Using data collected by the fixed target Fermilab experiment FOCUS, we present several first measurements for the semileptonic decay $D^0 \to \bar{K}^0π^-μ^+ν$. Using a model that includes a $\bar{K}^0 π^-$ S-wave component, we measure the form factor ratios to be r_v= 1.706+-0.677+-0.342 and r_2= 0.912+-0.370+-0.104 and the S-wave amplitude to be A=0.347+-0.222+-0.053 GeV^-1. Finally, we measure the vector semileptonic branching ratio $\frac{Γ(D^0 \to K^{*}(892){-}μ^+ν)}{Γ(D^0 \to \bar{K}^0π^-π^+)}= 0.337+-0.034+-0.013.

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arXiv2004

A Proposal for a Near Detector Experiment on the Booster Neutrino Beamline: FINeSSE: Fermilab Intense Neutrino Scattering Scintillator Experiment

Understanding the quark and gluon substructure of the nucleon has been a prime goal of both nuclear and particle physics for more than thirty years and has led to much of the progress in strong interaction physics. Still the flavor dependence of the nucleon's spin is a significant fundamental question that is not understood. Experiments measuring the spin content of the nucleon have reported conflicting results on the amount of nucleon spin carried by strange quarks. Quasi-elastic neutrino scattering, observed using a novel detection technique, provides a theoretically clean measure of this quantity. The optimum neutrino beam energy needed to measure the strange spin of the nucleon is 1 GeV. This is also an ideal energy to search for neutrino oscillations at high $Δm^2$ in an astrophysically interesting region. Models of the r-process in supernovae which include high-mass sterile neutrinos may explain the abundance of neutron-rich heavy metals in the universe. These high-mass sterile neutrinos are outside the sensitivity region of any previous neutrino oscillation experiments. The Booster neutrino beamline at Fermilab provides the world's highest intensity neutrino beam in the 0.5-1.0 GeV energy range, a range ideal for both of these measurements. A small detector located upstream of the MiniBooNE detector, 100 m from the recently commissioned Booster neutrino source, could definitively measure the strange quark contribution to the nucleon spin. This detector, in conjunction with the MiniBooNE detector, could also investigate $ν_μ$ disappearance in a currently unexplored, cosmologically interesting region.

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arXiv2004

Measurement of Masses and Widths of Excited Charm Mesons $D_2^*$ and Evidence for Broad States

Using data from the FOCUS experiment we analyze the $D^+π^-$ and $D^0π^+$ invariant mass distributions. We measure the $D_2^{*0}$ mass $M_{D_2^{*0}} = (2464.5 \pm 1.1 \pm 1.9) \mev$ and width $Γ_{D_2^{*0}} = (38.7 \pm 5.3 \pm 2.9) \mev$, and the $D_2^{*+}$ mass $ M_{D_2^{*+}} = (2467.6 \pm 1.5 \pm 0.76) \mev$ and width $ Γ_{D_2^{*+}} = (34.1 \pm 6.5 \pm 4.2) \mev$. We find evidence for broad structures over background in both the neutral and charged final state. If each is interpreted as evidence for a single L=1, $j_q=1/2$ excited charm meson resonance, the masses and widths are $M_{1/2}^0 =(2407 \pm 21 \pm 35) \mev$, $Γ_{1/2}^0 = (240 \pm 55 \pm 59) \mev$, and $M_{1/2}^+ = (2403 \pm 14 \pm 35) \mev$ $Γ_{1/2}^+ = (283 \pm 24 \pm 34) \mev$, respectively.

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arXiv2003

Study of Hadronic Five-Body Decays of Charmed Mesons Involving $K_S^0$

We study the decay of $D^0$ and $D^+_s$ mesons into five-body final states including a $K_S^0$ and report the discovery of the decay mode $D_s^+\to K_S^0 K_S^0π^+π^+π^-$. The branching ratio for the new mode is {${Γ(D_s^+\to K_S^0K_S^0π^+π^-π^+)} \over {Γ(D_s^+\to K_S^0K^-π^+π^+)}$} = 0.102$\pm0.029\pm$0.029. We also determine the branching ratio of {${Γ(D^0\to K_S^0π^+π^+π^-π^-)} \over {Γ(D^0 \to K_S^0π^+π^-)}$} = 0.095$\pm0.005\pm$0.007 as well as an upper limit for {${Γ(D^0\to K_S^0K^-π^+π^+π^-)} \over {Γ(D^0\to K_S^0π^+π^+π^-π^-)}$} $<$ 0.054 (90% CL). An analysis of the resonant substructure for $D^0 \to K_S^0π^+π^+π^-π^-$ is also performed.

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arXiv2003

Using Reactors to Measure $θ_{13}$

A next-generation neutrino oscillation experiment using reactor neutrinos could give important information on the size of mixing angle $θ_{13}$. The motivation and goals for a new reactor measurement are discussed in the context of other measurements using off-axis accelerator neutrino beams. The reactor measurements give a clean measure of the mixing angle without ambiguities associated with the size of the other mixing angles, matter effects, and effects due to CP violation. The key question is whether a next-generation experiment can reach the needed sensitivity goals to make a measurement for $\sin^{2}2θ_{13}$ at the 0.01 level. The limiting factors associated with a reactor disappearance measurement are described with some ideas of how sensitivities can be improved. Examples of possible experimental setups are presented and compared with respect to cost and sensitivity.

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arXiv2003

Measurements of $Ξ_c^{+}$ Branching Ratios

Using data collected by the fixed target Fermilab experiment FOCUS, we measure the branching ratios of the Cabibbo favored decays $Ξ_c^+ \to Σ^+K^-π^+$, $Ξ_c^+ \to Σ^+ \bar{K}^{*}(892)^0$, and $Ξ_c^+ \to Λ^0K^-π^+π^+$ relative to $Ξ_c^+ \to Ξ^-π^+π^+$ to be $0.91\pm0.11\pm0.04$, $0.78\pm0.16\pm0.06$, and $0.28\pm0.06\pm0.06$, respectively. We report the first observation of the Cabibbo suppressed decay $Ξ_c^+ \to Σ^+K^+K^-$ and we measure the branching ratio relative to $Ξ_c^+ \to Σ^+K^-π^+$ to be $0.16\pm0.06\pm0.01$. We also set 90% confidence level upper limits for $Ξ_c^+ \to Σ^+ ϕ$ and $Ξ_c^+ \to Ξ^*(1690)^0(Σ^+ K^-) K^+$ relative to $Ξ_c^+ \to Σ^+K^-π^+$ to be 0.12 and 0.05, respectively. We find an indication of the decays $Ξ_c^+ \to Ω^-K^{+}π^+$ and $Ξ_c^+ \to Σ^{*}(1385)^+ \bar{K}^0$ and set 90% confidence level upper limits for the branching ratios with respect to $Ξ_c^+ \to Ξ^-π^+π^+$ to be 0.12 and 1.72, respectively. Finally, we determine the 90% C.L. upper limit for the resonant contribution $Ξ_c^+ \to Ξ^{*}(1530)^0 π^+$ relative to $Ξ_c^+ \to Ξ^-π^+π^+$ to be 0.10.

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arXiv2003

Studies of correlations between D and ${\bar D}$ mesons in high energy photoproduction

Studies of $D{\bar D}$ correlations for a large sample of events containing fully and partially reconstructed pairs of charmed $D$ mesons recorded by the Fermilab photoproduction experiment FOCUS (FNAL-E831) are presented. Correlations between $D$ and ${\bar D}$ mesons are used to study heavy quark production dynamics. We present results for fully and partially reconstructed charm pairs and comparisons to a recent version of \textsc{Pythia} with default parameter settings. We also comment on the production of $ψ(3770)$ in our data.

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arXiv2003

Measurement of the $Ω_c^0$ Lifetime

The FOCUS experiment(FNAL-E831) has used two channels, $Ω^- π^+$ and $Ξ^-K^- π^+ π^+$,to measure the lifetime of the $Ω_c^0$ charmed baryon. From a sample of $64 \pm 14$ signal events at a mass of 2.698 GeV/$c^2$, we measure an $Ω_c^0$ lifetime of $72 \pm 11$ (stat.) $\pm 11$ (sys.) fs, substantially improving upon the current world average.

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arXiv2003

Charm System Tests of CPT and Lorentz Invariance with FOCUS

We have performed a search for CPT violation in neutral charm meson oscillations. While flavor mixing in the charm sector is predicted to be small by the Standard Model, it is still possible to investigate CPT violation through a study of the proper time dependence of a CPT asymmetry in right-sign decay rates for $D^0\to K^-π^+$ and $\d0b\to K^+π^-$. This asymmetry is related to the CPT violating complex parameter $ξ$ and the mixing parameters $x$ and $y$: $A_{CPT}\propto{\rm Re} ξy-{\rm Im} ξx$ . Our 95% confidence level limit is $-0.0068<{\rm Re} ξy-{\rm Im} ξx<0.0234$. Within the framework of the Standard Model Extension incorporating general CPT violation, we also find 95% confidence level limits for the expressions involving coefficients of Lorentz violation of $(-2.8<N(x,y,δ)(Δa_0 + 0.6 Δa_Z)<4.8)\times 10^{-16}$ GeV, $(-7.0<N(x,y,δ)Δa_X<3.8)\times 10^{-16}$ GeV, and $(-7.0<N(x,y,δ)Δa_Y<3.8)\times 10^{-16}$ GeV, where $N(x,y,δ)$ is the factor which incorporates mixing parameters $x$, $y$ and the doubly Cabibbo suppressed to Cabibbo favored relative strong phase $δ$.

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arXiv2002

A new measurement of the $Ξ_{c}^{0}$ lifetime

Using data collected by the Fermilab experiment FOCUS, we measure the lifetime of the charmed baryon (Ξ_{c}^{o}) using the decay channels (Ξ_{c}^{o}\to Ξ^{-}π^{+}) and (Ξ_{c}^{o}\to Ω^{-}K^{+}). From a combined sample of (110\pm 17) events we find (τ(Ξ_{c}^{o}) =~118^{+ 14}_{- 12} \pm5) fs, where the first and second errors are statistical and systematic, respectively.

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arXiv2002

Measurements of Relative Branching Ratios of $Λ_{c}^{+}$ Decays into States Containing $Σ$

We have studied the Cabibbo suppressed decay (Λ_{c}^{+}\to Σ^{+}K^{*0}(892)) and the Cabibbo favored decays (Λ_{c}^{+}\to Σ^{+}K^{+}K^{-}), (Λ_{c}^{+}\to Σ^{+}ϕ) and (Λ_{c}^{+}\to Ξ^{*0}(Σ^{+}K^{-})K^{+}) and measured their branching ratios relative to (Λ_{c}^{+}\to Σ^{+}π^{+}π^{-}) to be ((7.8\pm 1.8\pm 1.3)%), ((7.1\pm 1.1\pm 1.1)%), ((8.7\pm 1.6\pm 0.6)%) and ((2.2\pm 0.6\pm 0.6)%), respectively. The first error is statistical and the second is systematic. We also report two 90% confidence level limits (Γ(Λ_{c}^{+}\to Σ^{-}K^{+}π^{+})/Γ(Λ_{c}^{+}\to Σ^{+}K^{*0}(892))<35%) and (Γ(Λ_{c}^{+}\to Σ^{+}K^{+}K^{-})_{NR}/Γ(Λ_{c}^{+}\to Σ^{+}π^{+}π^{-})<2.8%).

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arXiv2002

A High Statistics Measurement of the Lambdac+ Lifetime

A high statistics measurement of the Lambdac+ lifetime from the Fermilab fixed-target FOCUS photoproduction experiment is presented. We describe the analysis technique with particular attention to the determination of the systematic uncertainty. The measured value of 204.6 +/- 3.4 (stat.) +/- 2.5 (syst.) fs from 8034 +/- 122 Lambdac -> pKpi decays represents a significant improvement over the present world average.

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arXiv2001

A measurement of branching ratios of $D^+$ and $D^+_s$ hadronic decays to four-body final states containing a $K_S$

We have studied hadronic four-body decays of $D^+$ and $D^+_s$ mesons with a $K_S$ in the final state using data recorded during the 1996-1997 fixed-target run at Fermilab high energy photoproduction experiment FOCUS. We report a new branching ratio measurement of $Γ(D^+\to K_S K^-π^+π^+)/Γ(D^+\to K_S π^+π^+π^-)=0.0768\pm0.0041\pm0.0032$. We make the first observation of three new decay modes with branching ratios $Γ(D^+\to K_S K^+π^+π^-)/Γ(D^+\to K_S π^+π^+π^-)=0.0562\pm0.0039\pm0.0040$, $Γ(D^+\to\K_S K^+ K^-π^+)/Γ(D^+\to K_S π^+π^+π^-)=0.0077\pm0.0015\pm0.0009$, and $Γ(D^+_s\to K_S K^+π^+π^-)/Γ(D^+_s\to K_S K^-π^+π^+)=0.586\pm0.052\pm0.043$, where in each case the first error is statistical and the second error is systematic.

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