Precise tests of low energy QCD from decay properties

Dipartimento di Fisica Sperimentale dell’Università e Sezione dell’INFN di Torino, 10125 Torino, Italy; University of Birmingham, Edgbaston, Birmingham, B15 2TT UK; Università di Roma “La Sapienza” e Sezzione dell’INFN di Roma, 00185 Roma, Italy; Department of Physics, Imperial College, London, SW7 2BW UK; Faculty of Physics, University of Sofia “St. Kl. Ohridski”, 1164 Sofia, Bulgaria; Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030, USA; Dipartimento di Fisica, Università di Modena e Reggio Emilia, 41100 Modena, Italy; Istituto di Fisica, Università di Urbino, 61029 Urbino, Italy; SLAC, Stanford University, Menlo Park, CA 94025, USA; Laboratory for High Energy Physics, 3012 Bern, Switzerland; UCLA, Los Angeles, CA 90024, USA; Laboratori Nazionali di Frascati, 00044 Frascati (Rome), Italy; Institut de Física d’Altes Energies, UAB, 08193 Bellaterra (Barcelona), Spain; Dipartimento di Fisica Sperimentale dell’Università di Torino, 10125 Torino, Italy; Institut de Physique Nucléaire de Lyon, IN2P3-CNRS, Université Lyon I, 69622 Villeurbanne, France; University College Dublin School of Physics, Belfield, Dublin 4, Ireland; Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, 28040 Madrid, Spain
European Physical Journal C (Impact Factor: 5.25). 01/2010; 70(3):635-657. DOI: 10.1140/epjc/s10052-010-1480-6

ABSTRACT We report results from the analysis of the $\mbox {$\mbox { ($\mbox {$\mbox {) decay by the NA48/2 collaboration at the CERN SPS, based on the total statistics of 1.13 million decays collected in 2003–2004.
The hadronic form factors in the S- and P-wave and their variation with energy are obtained. The phase difference between
the S- and P-wave states of the ππ system is accurately measured and allows a precise determination of $\mbox {$\mbox { and $\mbox {$\mbox {, the I = 0 and I = 2 S-wave ππ scattering lengths: $\mbox {$\mbox {. Combination of this result with the other NA48/2 measurement obtained in the study of $\mbox {$\mbox { decays brings an improved determination of $\mbox {$\mbox { and the first precise experimental measurement of $\mbox {$\mbox {, providing a stringent test of Chiral Perturbation Theory predictions and lattice QCD calculations. Using constraints based
on analyticity and chiral symmetry, even more precise values are obtained: $\mbox {$\mbox { and $\mbox {$\mbox {.

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    ABSTRACT: In order to investigate predictions concerning CP violation in the charged kaon sector, a new beam line providing concurrently K+ and K− has been constructed at CERN for the NA48/2 experiment. Several modifications and upgrades have been made in the apparatus; one of them being the implementation of a beam spectrometer named KABES. This detector is based on the time projection chamber principle; the amplification of the ionization signal is achieved by using Micromegas devices. The performance of KABES is found to be excellent in high-intensity hadron beams. The achieved space resolution of 100 μm provides a measurement of track momentum with a precision better than 1% and the time resolution, better than 1 ns, allows the charged kaons in NA48 to be identified with almost no ambiguity. The measurement of the direction and momentum of the K+ and K− tracks makes possible the precise study of their decay modes, particularly those for which one or more particles escape detection in the NA48 detector.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2004; · 1.14 Impact Factor
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    ABSTRACT: We present the first results of the PACS-CS project which aims to simulate 2+1 flavor lattice QCD on the physical point with the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action. Numerical simulations are carried out at the lattice spacing of $a=0.0907(13)$fm on a $32^3\times 64$ lattice with the use of the DDHMC algorithm to reduce the up-down quark mass. Further algorithmic improvements make possible the simulation whose ud quark mass is as light as the physical value. The resulting PS meson masses range from 702MeV down to 156MeV, which clearly exhibit the presence of chiral logarithms. An analysis of the PS meson sector with SU(3) ChPT reveals that the NLO corrections are large at the physical strange quark mass. In order to estimate the physical ud quark mass, we employ the SU(2) chiral analysis expanding the strange quark contributions analytically around the physical strange quark mass. The SU(2) LECs ${\bar l}_3$ and ${\bar l}_4$ are comparable with the recent estimates by other lattice QCD calculations. We determine the physical point together with the lattice spacing employing $m_\pi$, $m_K$ and $m_\Omega$ as input. The hadron spectrum extrapolated to the physical point shows an agreement with the experimental values at a few % level of statistical errors, albeit there remain possible cutoff effects. We also find that our results of $f_\pi=134.0(4.2)$MeV, $f_K=159.4(3.1)$MeV and $f_K/f_\pi=1.189(20)$ with the perturbative renormalization factors are compatible with the experimental values. For the physical quark masses we obtain $m_{\rm ud}^\msbar=2.527(47)$MeV and $m_{\rm s}^\msbar=72.72(78)$MeV extracted from the axial-vector Ward-Takahashi identity with the perturbative renormalization factors. Comment: 43 pages, 48 figures
    Physical Review D 07/2008; · 4.69 Impact Factor
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    ABSTRACT: We have calculated the form-factors F and G in K→ππℓν decays (Kℓ4) to two-loop order in Chiral Perturbation Theory (ChPT). Combining this together with earlier two-loop calculations an updated set of values for the Lir, the ChPT constants at , is obtained. We discuss the uncertainties in the determination and the changes compared to previous estimates.
    Physics Letters B 12/1999; · 4.57 Impact Factor

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