93247228
Measurement of the strong interaction shift and width of the 1S levels in pionic hydrogen and deuterium
92019819
Kinetic Energy Distribution of $\pi^{-}p$ Atoms in Liquid and Gaseous Hydrogen
63344758
MDT Commissioning Procedures Guidelines for Certifying RFI Chambers
123875509
The strong interaction shift and width of the ground state of pionic hydrogen
Abstract The 3p-1s transition in pionic hydrogen was investigated with a high-resolution crystal spectrometer system. From the precisely measured transition energy, together with the (calculated) electromagnetic energy, the strong interaction shift of the 1s state was obtained as ϵ 1s = −7.127 ± 0.028(stat.)± 0.036(syst.) eV (attractive). From the natural line width, measured for the first time, we determine the decaywidth of the 1s state: Γ 1s (decay) = 0.97 ± 0.10(stat.)± 0.05(syst.) eV. With the recently calculated electromagnetic corrections the s-wave scattering lengths of an isospin symmetric strong interaction are deduced. The scattering length for elastic scattering of a negative pion on a proton is a π − p → π − p h = 0.0885±0.00003(stat.)±0.0006(syst.) m π −1 . The scattering lengthe for single charge exchange is found to be a π − p → π 0 n h = −0.136 ± 0.007(stat.) ± 0.003(syst.) m π −1 . The experiment was performed at the Paul Scherrer Institute (PSI) in Switzerland. A focussing crystal spectrometer with an array of bent crystals, the cyclotron trap (a magnetic system designed to increase the particle stop density) and a CCD (charge-coupled device) detector system were employed. The results from the pionic hydrogen experiment — together with those from the pionic deuterium experiment — were used to test the isospin symmetry of the strong interaction. The present data are still consistent with isospin sysmmetry.
120397351
BESIII status and recent results
We report the status of BESIII at BEPCII and recent results from 106M ψ′ and 226M J/ψ samples at BESIII. These results include the confirmation of X (1860) in ψ′→π+π−J/ψ(J/ψ→γpp) from ψ′ sample and J/ψ→γpp from J/ψ samples, and X (1835) in J/ψ→γη′ππ., the suty of a0(980) - f0(980) mixing, as well as the preliminary results on the excited baryon states. The physics potentials, especially that for the baryon physics program at BESIII are also mentioned briefly.
12460113
R-VALUES FROM LOW ENERGY e+e- ANNIHILATION
The QED running coupling constant α(s) and the anomalous magnetic moment of muon aμ are two fundamental quantities for the precision test of the Standard Model (SM). The current uncertainties on α(s) and aμ are dominated by the contribution from the R-values measured about 20 years ago with an averaged uncertainty of 15% in the energy region below 5 GeV. This review article summarizes the recent measurements of R-values in low energy e+e- annihilation. The new experiments aimed at reducing the uncertainties in R-values and performed with the upgraded Beijing Spectrometer (BESII) at Beijing Electron Positron Collider (BEPC) in Beijing and with Cryogenic Magnetic Detector, CMD-2 and SND (Spherical Neutral Detector) at VEEP-2M in Novosibirsk are reviewed and discussed.
118594305
Realizing tri-bimaximal mixing in minimal seesaw model with S4 family symmetry
In this Letter, we realize the tri-bimaximal mixing in the lepton sector in the context of minimal seesaw in which only two right-handed neutrinos are introduced, with the discrete group S4 as the family symmetry. In order to constrain the form of superpotential, a Z3 symmetry is also introduced. In the model, the mass matrices for charged leptons and right-handed neutrinos are diagonal. The unitary matrix that diagonalizes the light Majorana neutrino mass matrix is exact tri-bimaximal at LO, and is corrected by small quantities of O(0.01) at NLO. The mechanism to get the particular scalar VEV alignments used is also presented. Phenomenologically, the mass spectrum is of normal hierarchy with m(1) = 0, and Sigma m(i) and vertical bar m(ee)vertical bar are about 0.058 eV and 0.003 eV respectively. (C) 2011 Elsevier B.V. All rights reserved.
53134693
Minimal modifications to the Tri-Bimaximal neutrino mixing
A bstractIn light of the observation of a relatively large θ13, the ever popular Tri-Bimaximal (TBM) neutrino mixing which predicts a vanishing θ13 needs modifications. In this paper, we shall discuss the possibility of modifying it in a minimal way to fulfil this task. In the first part, a neutrino mass matrix with three independent parameters, which leads to the TM2 mixing, is obtained by analogy with that for the TBM mixing. In the second part, a model that can realize the TM2 mixing is constructed with flavor symmetries A4 × U(1) × Z2 × Z2 × Z2. It is the variant of a model that gives the TBM mixing, with only one more flavon field included. Furthermore, the imaginary vacuum expectation value (VEV) of this flavon breaks the imposed CP symmetry and results in θ23 = 45° and the maximal CP violation. Besides, this model building approach can be generalized to the TM1 mixing in a straightforward way.
119280451
Understanding for flavor physics in the lepton sector
In this paper, we give a model for understanding flavor physics in the lepton sector mass hierarchy among different generations and neutrino mixing patterns. The model is constructed in the framework of supersymmetry, with a family symmetry S4 * U(1). There are two right-handed neutrinos introduced for a seesaw mechanism, while some standard model gauge group singlet fields are included, which transforms nontrivially under family symmetry. In the model, each order of contributions are suppressed by delta similar to 0.1 compared to the previous one. In order to reproduce the mass hierarchy, m(tau) and root Delta m(atm)(2), and m(mu) and root Delta m(sol)(2) are obtained at leading order and next-to-leading order, respectively, while the electron can only get its mass through next-to-next-to-next-to-leading order contributions. For neutrino mixing angels, theta(12), theta(23), theta(13) are 45 degrees, 45 degrees, 0, i.e., the bimaximal mixing pattern as a first approximation, while higher order contributions can make them consistent with experimental results. As corrections for theta(12) and theta(13) originate from the same contribution, there is a relation predicted for them: sin theta(13) 1-tan theta(12)/1+tan theta(12). Besides, the deviation from pi/4 for theta(23) should have been as large as the deviation from 0 for theta(13;) if not, the former is suppressed by a factor of 4 compared to the latter.
119257528
MINOS anomaly as a signal of Lorentz violation
Recently, the MINUS Collaboration reported an anomaly that the mass-squared difference and mixing angle of (v) over bar (mu) (v) over bar (tau) are both different from that of (v) over bar (mu) (v) over bar (tau) . In this Letter, based on the framework of neutrino oscillations, terms that break the Lorentz symmetry are used as perturbation to explain this anomaly and satisfactory results are got. Remarkably, some surprising conclusions, one of which is that in the high energy limit (hundreds of GeV) neutrino oscillation pattern will be independent of energy, are also arrived. (C) 2011 Elsevier B.V. All rights reserved.