121652994
The Qweak: Precision Measurement of the Proton’s Weak Charge by Parity Violating Experiment
The Qweak experiment at the Thomas Jefferson National Accelerator Facility measures the parity violating asymmetry in longitudinally polarized electron scattering from the proton at very low momentum transfer, Q2 = 0.026 (GeV/c)2, at an incident electron beam energy of 1.16 GeV. With this measurement and the earlier results of the parity violating elastic scattering experiments, the Qweak experiment determines the weak charge of the proton, $${Q^p_{\rm W}}$$, with a 4% combined statistical and systematic error. This measurement will be used to determine the weak mixing angle, $${\sin^2\theta_{\rm W}}$$, that is predicted by the Standard Model from the Z0 pole down to lower energies. Qweak will determine $${\sin^2\theta_{\rm W}}$$ to a 0.3% relative precision, providing a competitive measurement of the running of this quantity. Moreover, if there is a significant deviation of the weak mixing angle from the Standard Model prediction, then the Qweak experiment will give a glimpse of possible extensions of the Standard Model.
208868561
A high power liquid hydrogen target for the Mainz A4 parity violation experiment
Abstract We present a new powerful liquid hydrogen target developed for the precise study of parity violating electron scattering on hydrogen and deuterium. This target has been designed to have minimal target density fluctuations under the heat load of a 20 μ A CW 854.3 MeV electron beam without rastering the electron beam. The target cell has a wide aperture for scattered electrons and is axially symmetric around the beam axis. The construction is optimized to intensify heat exchange by a transverse turbulent mixing in the hydrogen stream, which is directed along the electron beam. The target is constructed as a closed loop circulating system cooled by a helium refrigerator. It is operated by a tangential mechanical pump with an optional natural convection mode. The cooling system supports removal of up to 250 W of beam heating removal. Deeply subcooled liquid hydrogen is used to keep the in-beam temperature below the boiling point. The target density fluctuations are found to be at the level of 10 - 3 at a beam current of 20 μ A .
121363109
Status of Rare Isotope Science Project in Korea
The Rare Isotope Science Project (RISP) is launched in Korea to build the IF and ISOL facilities. Current status of RISP is introduced.
6220935
Measurement of the neutron radius of 208Pb through parity violation in electron scattering.
We report the first measurement of the parity-violating asymmetry A(PV) in the elastic scattering of polarized electrons from 208Pb. A(PV) is sensitive to the radius of the neutron distribution (R(n)). The result A(PV)=0.656±0.060(stat)±0.014(syst) ppm corresponds to a difference between the radii of the neutron and proton distributions R(n)-R(p)=0.33(-0.18)(+0.16) fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.
120231751
Electron beam line design of A4 Compton backscattering polarimeter
The new beam line has been built to measure the polarization of the electron. The transverse position and emittance of the MAMI beam are determined from measurements of the beam size on three wire scanners. The position measurement has been done and the emittance measurement is still progressing.PACS: 29.27.Eg Beam handling; beam transport – 29.27.Fh Beam characteristics
126156206
Concept and Realization of the A4 Compton Backscattering Polarimeter at MAMI
5890165
Measurement of the W boson mass with the Collider Detector at Fermilab
We present a measurement of the W boson mass using data collected with the CDF detector during the 1994-1995 collider run at the Fermilab Tevatron. A fit to the transverse mass spectrum of a sample of 30115 W --> ev events recorded in an integrated luminosity of 84 pb(-1) gives a mass M-W=80.473 +/-0.065(stat) +/-0.092(syst) GeV/c(2). A fit to the transverse mass spectrum of a sample of 14740 W --> muv events from 80 pb(-1) gives a mass M-W=80,465 +/-0.100(stat)+/-0.103(syst) Ge V/c(2) The dominant contributions to the systematic uncertainties are the uncertainties in the electron energy scale and the muon momentum scale, 0.075 GeV/c(2) and 0.085 GeV/c(2), respectively. The combined value for the electron and muon channel is M-W=80.470 +/-0.089-GeV/c(2). When combined with previously published CDF measurements, we obtain M-W=80.433 +/-0.079 GeV/c(2).
118342811
LONG-TERM PHOTOMETRIC BEHAVIOR OF THE ECLIPSING BINARY GW CEPHEI
New CCD photometry over four successive years from 2005 is presented for the eclipsing binary GW Cep, together with reasonable explanations for the light and period variations. All historical light curves, obtained over a 30 yr interval, display striking light changes, and are best modeled by the simultaneous existence of a cool spot and a hot spot on the more massive cool component star. The facts that the system is magnetically active and that the hot spot has consistently existed on the inner hemisphere of the star indicate that the two spots are formed by (1) magnetic dynamo-related activity on the cool star and (2) mass transfer from the primary to the secondary component. Based on 38 light-curve timings from the Wilson-Devinney code and all other minimum epochs, a period study of GW Cep reveals that the orbital period has experienced a sinusoidal variation with a period and semi-amplitude of 32.6 yr and 0.009 days, respectively. In principle, these may be produced either by a light-travel-time effect due to a third body or by an active magnetic cycle of at least one component star. Because we failed to find any connection between luminosity variability and the period change, that change most likely arises from the existence of an unseen third companion star with a minimum mass of 0.22 M ☉ gravitationally bound to the eclipsing pair.
119087481
Optimal spin quantization axes for quarkonium with large transverse momentum
The gluon collision process that creates a heavy-quark-antiquark pair with small relative momentum and large transverse momentum predicts at leading-order in the QCD coupling constant that the transverse polarization of the pair should increase with its transverse momentum. Measurements at the Fermilab Tevatron of the polarization of charmonium and bottomonium states with respect to a particular spin-quantization axis are inconsistent with this prediction. However the predicted rate of approach to complete transverse polarization depends on the choice of spin-quantization axis. We introduce axes that maximize and minimize the transverse polarization from the leading-order gluon collision process. They are determined by the direction of the jet that provides most of the balancing transverse momentum.
202105722
Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC
A search for microscopic black holes has been performed in a same-sign dimuon final state using 1.3 fb(-1) of proton-proton collision data collected with the ATLAS detector at a centre of mass energy of 7 TeV at the CERN Large Hadron Collider. The data are found to be consistent with the expectation from the Standard Model and the results are used to derive exclusion contours in the context of a low scale gravity model.
119074454
Weakly-bound Hadronic Molecule near a 3-body Threshold
The X(3872) seems to be a loosely-bound hadronic molecule whose constituents are two charm mesons. A novel feature of this molecule is that the mass difference of the constituents is close to the mass of a lighter meson that can be exchanged between them, namely, the pion. We analyze this feature in a simple model with spin-0 mesons only. Various observables are calculated to next-to-leading order in the interaction strength of the exchanged meson. Renormalization requires summing a geometric series of next-to-leading order corrections. The dependence of observables on the ultraviolet cutoff can be removed by renormalizations of the mass of the heaviest meson, the coupling constant for the contact interaction between the heavy mesons, and short-distance coefficients in the operator product expansion. The next-to-leading order correction has an unphysical infrared divergence at the threshold of the two heavier mesons that can be eliminated by a further resummation that takes into account the nonzero width of the heaviest meson.