In order to improve existing I=0 phase shift solutions, the spin correlation parameter ANN and the analyzing powers A0N and AN0 have been measured in n-p elastic scattering over an angular range of 50°–150° (c.m.) at three neutron energies (220, 325, and 425 MeV) to an absolute accuracy of ±0.03. The data have a profound effect on various phase parameters, particularly the P11, D23, and ε1 phase parameters which in some cases change by almost a degree. With the exception of the highest energy, the data support the predictions of the latest version of the Bonn potential. Also, the analyzing power data (A0N and AN0) measured at 477 MeV in a different experiment over a limited angular range [60°–80° (c.m.)] are reported here.
The beam analysing power at incident kinetic energy 220 MeV. Additional systematic uncertainty of +- 0.015 and a scalar error of 3.5 PCT.
The beam analysing power at incident kinetic energy 325 MeV. Additional systematic uncertainty of +- 0.018 and a scalar error of 3.1 PCT.
The beam analysing power at incident kinetic energy 425 MeV. Additional systematic uncertainty of +- 0.022 and a scalar error of 3.3 PCT.
The effect of isospin-violating, charge-symmetry-breaking (CSB) terms in the np interaction has been observed at TRIUMF by measuring the difference in the zero-crossing angles of the neutron and proton analyzing powers, An and Ap, at a neutron energy of 477 MeV. The scattering asymmetries were measured with a neutron beam incident on a polarizable proton target. To reduce systematic errors, interleaved measurements of An and Ap were made using the same beam and target (apart from their respective polarization states). Neutrons and protons were detected in coincidence in the center-of-mass angle range from 59°–80°. The difference in zero-crossing angles was 0.340°±0.162° (±0.058°), which yields ΔA≡An-Ap=0.0047±0.0022 (±0.0008) using dA/dθc.m.=−0.01382 deg−1. The second errors represent systematic effects. This result is in good agreement with recent theoretical calculations which include CSB effects due to the np mass difference in π, ρ, and 2π exchange, electromagnetic coupling of the neutron anomalous magnetic moment to the proton current, ρ-ω-meson mixing, and short- and medium-range effects of the up- and down-quark mass difference.
No description provided.
A search is presented for heavy bosons decaying to Z($\nu\bar{\nu}$)V(qq'), where V can be a W or a Z boson. A sample of proton-proton collision data at $\sqrt{s} =$ 13 TeV was collected by the CMS experiment during 2016-2018. The data correspond to an integrated luminosity of 137 fb$^{-1}$. The event categorization is based on the presence of high-momentum jets in the forward region to identify production through weak vector boson fusion. Additional categorization uses jet substructure techniques and the presence of large missing transverse momentum to identify W and Z bosons decaying to quarks and neutrinos, respectively. The dominant standard model backgrounds are estimated using data taken from control regions. The results are interpreted in terms of radion, W' boson, and graviton models, under the assumption that these bosons are produced via gluon-gluon fusion, Drell-Yan, or weak vector boson fusion processes. No evidence is found for physics beyond the standard model. Upper limits are set at 95% confidence level on various types of hypothetical new bosons. Observed (expected) exclusion limits on the masses of these bosons range from 1.2 to 4.0 (1.1 to 3.7) TeV.
Simulated distributions are shown for the cosine of the decay angle of SM vector bosons in the rest frame of a parent particle with a mass (mX) of 2\TeV. Solid lines represent VBF scenarios. Dashed lines represent ggF/DY scenarios.
Distributions of mT for ggF/DY-produced resonances X of mass 4.5 TeV.
Distributions of mT for VBF-produced resonances X of mass 4.5 TeV.
The associated production of a W and a Z boson is studied in final states with multiple leptons produced in proton-proton (pp) collisions at a centre-of-mass energy of 13 TeV using 137 fb$^{-1}$ of data collected with the CMS detector at the LHC. A measurement of the total inclusive production cross section yields $\sigma_{\text{tot}}$(pp $\to$ WZ) = 50.6 $\pm$ 0.8 (stat) $\pm$ 1.5 (syst) $\pm$ 1.1 (lumi) $\pm$ 0.5 (theo) pb. Measurements of the fiducial and differential cross sections for several key observables are also performed in all the final-state lepton flavour and charge compositions with a total of three charged leptons, which can be electrons or muons. All results are compared with theoretical predictions computed up to next-to-next-to-leading order in quantum chromodynamics plus next-to-leading order in electroweak theory and for various sets of parton distribution functions. The results include direct measurements of the charge asymmetry and the W and Z vector boson polarization. The first observation of longitudinally polarized W bosons in WZ production is reported. Anomalous gauge couplings are searched for, leading to new constraints on beyond-the-standard-model contributions to the WZ triple gauge coupling.
Distribution of the three leading leptons flavour in the CR-ZZ with uncertainties evaluated after the inclusive cross section fit
Distribution of the jet multiplicity in the CR-ttZ with uncertainties evaluated after the inclusive cross section fit
Distribution of the three leading leptons flavour in the CR-conv with uncertainties evaluated after the inclusive cross section fit
Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $\pi^0$ and $\eta$ production in $\sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisions. Comparison of the $\pi^0$ results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, $\Delta G$, in the proton in the probed Bjorken $x$ range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}} = 0.06^{+0.11}_{-0.15}$ in the range $0.05<x<0.2$, with the uncertainty at $\Delta \chi^2 = 9$ when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}}$ between $0.02$ and $0.12$, demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.
PI0 ASYM(LL) measurements from 2005.
PI0 ASYM(LL) measurements from 2006.
PI0 ASYM(LL) measurements from 2009.
A measurement of Δσ L (np), the difference between neutron-proton total cross sections in pure longitudinal spin states, is described. Data were taken for five energies between 500 and 800 MeV, with statistical errors of ≈ 1.5 mb and an estimated normalization error of 6%. The data, combined with other results, show some evidence for an elastic I =0 spin-singlet resonance with mass ∼ 2213 MeV and width ∼ 74 MeV, or a coupled-triplet resonance with similar mass and width.
SIG(C=PARALLEL)-SIG(C=ANTIPARALLEL) means the difference in the total crosssection with initial parallel and antiparallel longitudinal spin states. The I0 means I=0, these values were found using interpolated Delta(sigma(pp)) data.
High quality analyzing powers for the π−p→→π0n reaction have been obtained with a polarized proton target over a broad angular range at incident kinetic energies of 98.1, 138.8, 165.9, and 214.4 MeV. This experiment nearly doubled the existing πN single-charge-exchange database for energies ranging from 10 to 230 MeV, with 36 new analyzing powers. The Neutral Meson Spectrometer was used to detect the outgoing neutral pions. The data are well described by recent phase-shift analyses. When combined with high-precision and accurate cross section data at the same energies, the data can provide a good test of the degree of isospin breaking in the region of the Δ(1232) resonance. They will also be helpful for constraining the evaluation of the pion-nucleon σ term from the scattering amplitudes.
First error is total uncertainty.
First error is total uncertainty.
First error is total uncertainty.
Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.
Measured beam asymmetry at photon energy 724 MeV as a function of the ETA centre of mass angle.
Measured beam asymmetry at photon energy 761 MeV as a function of the ETA centre of mass angle.
Measured beam asymmetry at photon energy 810 MeV as a function of the ETA centre of mass angle.
We have measured the analyzing power ANO and the spin transfer KNN for np-elastic scattering from about 60° to 170° c.m. at 485, 635, and 788 MeV. The new data clarify previous discrepancies and complete the first-order determination of nucleon-nucleon elastic scattering at these energies.
For definition of the POL(NAME=SPIN-TRANSFER) see text.
For definition of the POL(NAME=SPIN-TRANSFER) see text.
For definition of the POL(NAME=SPIN-TRANSFER) see text.
The reactions gamma p --> K+ Lambda and gamma p --> K+ Sigma0 were measured in the energy range from threshold up to a photon energy of 2.6 GeV. The data were taken with the SAPHIR detector at the electron stretcher facility, ELSA. Results on cross sections and hyperon polarizations are presented as a function of kaon production angle and photon energy. The total cross section for Lambda production rises steeply with energy close to threshold, whereas the Sigma0 cross section rises slowly to a maximum at about E_gamma = 1.45 GeV. Cross sections together with their angular decompositions into Legendre polynomials suggest contributions from resonance production for both reactions. In general, the induced polarization of Lambda has negative values in the kaon forward direction and positive values in the backward direction. The magnitude varies with energy. The polarization of Sigma0 follows a similar angular and energy dependence as that of Lambda, but with opposite sign.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 0.9 to 1.0 GeV.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.0 to 1.2 GeV.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.2 to 1.4 GeV.
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