Publications (5)14.74 Total impact
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Article: Search for CP violation in D± meson decays to ϕπ±.
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ABSTRACT: We search for CP violation in Cabibbo-suppressed charged D meson decays by measuring the difference between the CP-violating asymmetries for the Cabibbo-suppressed decays D(±)→K(+)K(-)π(±) and the Cabibbo-favored decays D(s)(±)→K(+)K(-)π(±) in the K(+)K(-) mass region of the ϕ resonance. Using 955 fb(-1) of data collected with the Belle detector, we obtain A(CP)(D+→ϕπ+)=(+0.51±0.28±0.05)%. The measurement improves the sensitivity of previous searches by more than a factor of 5. We find no evidence for direct CP violation.Physical Review Letters 02/2012; 108(7):071801. · 7.37 Impact Factor -
Article: Nuclear transparency and effective kaon-nucleon cross section from the A(e, e'K+) reaction
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ABSTRACT: We have determined the transparency of the nuclear medium to kaons from $A(e,e^{'} K^{+})$ measurements on $^{12}$C, $^{63}$Cu, and $^{197}$Au targets. The measurements were performed at the Jefferson Laboratory and span a range in four-momentum-transfer squared Q$^2$=1.1 -- 3.0 GeV$^2$. The nuclear transparency was defined as the ratio of measured kaon electroproduction cross sections with respect to deuterium, ($\sigma^{A}/\sigma^{D}$). We further extracted the atomic number ($A$) dependence of the transparency as parametrized by $T= (A/2)^{\alpha-1}$ and, within a simple model assumption, the in-medium effective kaon-nucleon cross sections. The effective cross sections extracted from the electroproduction data are found to be smaller than the free cross sections determined from kaon-nucleon scattering experiments, and the parameter $\alpha$ was found to be significantly larger than those obtained from kaon-nucleus scattering. We have included similar comparisons between pion- and proton-nucleon effective cross sections as determined from electron scattering experiments, and pion-nucleus and proton-nucleus scattering data.03/2011; -
Article: Experimental study of the A(e,e′π+) reaction on 1H, 2H, 12C, 27Al, 63Cu, and 197Au
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ABSTRACT: Cross sections for the 1H(e,e′π+)n process on 1H, 2H, 12C, 27Al, 63Cu, and 197Au targets were measured at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) to extract nuclear transparencies. Data were taken from Q2=1.1–4.7 GeV2 for a fixed center-of-mass energy of W=2.14 GeV. The ratio of σL and σT was extracted from the measured cross sections for 1H, 2H, 12C, and 63Cu targets at Q2=2.15 and 4.0 GeV2, allowing for additional studies of the reaction mechanism. In this article, we present the experimental setup and the analysis of the data in detail, including systematic uncertainty studies. Differential cross sections and nuclear transparencies as a function of the pion momentum at different values of Q2 are presented. Our results are consistent with the predicted early onset of color transparency in mesons. Global features of the data are discussed and the data are compared with model calculations for the 1H(e,e′π+)n reaction from nuclear targets.Phys. Rev. C. 05/2010; 81(5). -
Article: Measurement of nuclear transparency for the A(e,e'pi+) reaction.
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ABSTRACT: We have measured the nuclear transparency of the A(e,e'pi+) process in 2H, 12C, 27Al, 63Cu, and 197Au targets. These measurements were performed at the Jefferson Laboratory over a four momentum transfer squared range Q2=1.1 to 4.7 (GeV/c)2. The nuclear transparency was extracted as the super-ratio of (sigmaA/sigmaH) from data to a model of pion-electroproduction from nuclei without pi-N final-state interactions. The Q2 and atomic number dependence of the nuclear transparency both show deviations from traditional nuclear physics expectations and are consistent with calculations that include the quantum chromodynamical phenomenon of color transparency.Physical Review Letters 01/2008; 99(24):242502. · 7.37 Impact Factor -
Article: Scaling study of the pion electroproduction cross sections
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ABSTRACT: The 1H(e, e'π+)n cross section was measured for arange of four-momentum transfer up to Q2=3.91 GeV2 at values of the invariant mass W above the resonance region. The Q2 dependence of the longitudinal component was found to be consistent with the Q2-scaling prediction for hard exclusive processes. This suggests that the QCD factorization theorem is applicable at rather low values of Q2. The transverse term falls off slower than the naive Q-8 expectation and remains appreciable even at Q2=3.91 GeV2.Phys. Rev. C. 78(5).
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Institutions
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2010
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Tohoku University
Sendai, Kagoshima-ken, Japan
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2008
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Massachusetts Institute of Technology
- Laboratory for Nuclear Science
Cambridge, MA, USA
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