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1.
A formalism of the invariant spin amplitudes of the pd-scattering process in the Madison frame of reference is developed. The condition for T invariance with conservation of P-parity is formulated in terms of these amplitudes, and the relationships between differential spin observables that follow from this condition, are derived. The relative efficiency of the method for testing T-invariance on the basis of these relationships is compared to the method based on recording a null-test signal in an experiment with a polarized proton beam and the deuteron target.  相似文献   

2.
We report on the status of an extensive program to study the scattering of longitudinally polarized electrons from longitudinally polarized NH3 and ND3 targets using the CLAS detector at JLab. The data span a range inQ 2 from 0.05–4.5 (GeV/c)2 and a range inW, the γ* N invariant mass, up to about 3 GeV. With the excellent particle identification available with the CLA, both inclusive and exclusive scattering can be studied. The experimental techniques are reviewed and some preliminary results are presented. This paper focuses on extraction of the spin structure functiongg 1 for the proton and the deuteron.  相似文献   

3.
Double polarization asymmetry Dp(M) for the process of elastic electroweak scattering of the longitudinally polarized electrons by polarized proton target is considered with account of anapole G1p and electric dipole moment (EDM) G2p proton form factors. This asymmetry is only due to T-parity violating form factor G2p, but does not directly depend on it, and having a significant value, allows to confirm the existence of the EDM of the proton.  相似文献   

4.
Experimental data on inclusive deuteron production in 16Op collisions at high energies were obtained for the first time under conditions of 4π geometry. An irregularity in the momentum spectrum of deuterons in the rest frame of oxygen nuclei is found in the range 0.40 ≤ p ≤ 0.55 GeV/c, and the reasons for its appearance are discussed. The mean multiplicities of secondary fragments are correlated with the presence of deuterons in an event, these correlations being positive for fragments of charge in the range z f ≤ 4 and negative for fragments of charge in the range 5 ≤ z f ≤ 7. This is likely to be due to baryon-charge conservation.  相似文献   

5.
6.
The Hermes experiment at the Desy laboratory in Hamburg, Germany, studies the spin structure of the nucleon. Its unique feature is the combination of a polarized internal gas target with the longitudinally polarized 27.5 GeV electron/positron beam of the Hera accelerator. Recent Hermes measurements include the proton spin structure function g 1 p , the flavor decomposition of the polarized quark distributions in the nucleon, the DIS contribution to the generalized GDH sum rule, the first observation of a spin asymmetry in exclusive vector meson production and the first observation of a single-spin azimuthal asymmetry in semi-inclusive pion production. Additionally, the possibility of using various unpolarized gases as target material broadens the spectrum of physics measurements with Hermes.  相似文献   

7.
Significant baryon over meson enhancement was measured at RHIC in the intermediate transverse momentum range of p T =2?4 GeV/c (“baryon-meson puzzle”). With STAR detector we were able to extend particle identification towards higher transverse momentum offering further insights into the particle production mechanisms at intermediate to high p T . In this paper we present results on charged pion, proton and anti-proton spectra and ratios at intermediate to high p T exploiting the relativistic rise of the specific ionization energy loss measured in the STAR Time Projection Chamber. These measurements provide valuable information about the production mechanisms of particles at intermediate p T in relativistic heavy ion collisions, e.g. coalescence/recombination versus jet fragmentation.  相似文献   

8.
The primary goal of the HERMES experiment is the study of the spin structure of the nucleon. Results on the measured inclusive and semi-inclusive hadron asymmetries using a polarized positron beam on polarized 3He, hydrogen and deuterium targets are here presented. In the covered kinematic range, 0.023<x Bj <0.6 and 1 GeV2<Q 2<10GeV2 the polarized quark distribution were determined for all up (u+?u) and down (d+?) quarks, and separately for valence and sea quarks. The up quark polarization is positive, and the down quark polarization is negative. The polarization of the sea is consistent with zero in the measured range. A first indication of a positive gluon polarization is presented, based on the measured spin asymmetry in the photo-production of hadron pairs with high transverse momentum p T . This asymmetry is negative, which is in contrast to the measured positive asymmetry for inclusive experiments.  相似文献   

9.
Relative yields of high-x F charged hadrons (π ±, К±, р, \(\overline p \), and d) in proton–nucleus interactions at incident-proton momenta of 25 and 50 GeV/c were measured at an angle of 0° in the momentum range between 15 and 40 GeV/c. An upper limit on the forward production of two protons in proton–nucleus interactions at 50 GeV/c was estimated. The properties of a carbon beam with an energy of 25 GeV per nucleon and fragment yields in its interaction with nuclear targets were measured within a short exposure.  相似文献   

10.
The STAR experiment provides measurements of single and double-spin asymmetries in longitudinally and transversely polarized p + p collisions at \(\sqrt s \) = 200 and 510 GeV to deepen our understanding on the proton spin structure and dynamics of parton interactions over a wide range of collision energy, momentum and rapidity of the various produced probes. Polarized processes with W± production allow us to study the spin-flavor structure of the proton. Recent results obtained by STAR on the double longitudinal asymmetry, ALL, of pion and jet production at \(\sqrt s \) = 200 and 510 GeV, the single longitudinal, AL, and transverse, AN, asymmetry of W± production at \(\sqrt s \) = 510 GeV are overviewed. STAR results on azimuthal single transverse asymmetry of pion in p + (p, Au) and jet + π± in p + p collisions are discussed. The proposed Forward Calorimeter System (FCS) and Forward Tracking System (FTS) upgrades at STAR would significantly improve the capabilities of existing detectors for measurements of observables such as asymmetries of pion, jet, Drell-Yan pairs produced at forward rapidities.  相似文献   

11.
The two major pillars of searches for the Quark Gluon Plasma have been: J/Ψ suppression, proposed in 1986, and observed at both SPS fixed target energies and at RHIC; and, more recently, the suppression of π 0 with p T ≥3 GeV/c by a factor ~5 in Au+Au central collisions, observed at RHIC in 2001, which had been predicted in advance as a consequence of Landau-Pomeranchuck-Migdal coherent (gluon) bremsstrahlung by the outgoing hard-scattered partons traversing the medium. However, new effects were discovered and the quality of the measurements greatly improved so that the clarity of the original explanations has become obscured. For instance: J/Ψ suppression is the same at SpS and RHIC. Is it the QGP, comovers, something else? QCD provides beautiful explanations of π 0 and direct γ measurements in p–p collisions but precision fits of the best theories of π 0 suppression barely agree with the Au+Au data. Better data are needed for 10<p T <20 GeV/c, systematic errors are needed in theory calculations, the values of parameters of the medium such as \(\langle\hat{q}\rangle\) derived from precision fits are the subject of controversy. Baryons are much less suppressed than mesons, leading to an anomalous \(\bar{p}/\pi\) ratio for 2≤p T ≤4.5 GeV/c, but beautiful theoretical explanations of the effect such as recombination do not work in detail. Heavy quarks seem to be suppressed the same as the light quarks, naively arguing against the bremsstrahlung explanation and suggesting exotic, possible transformational explanations. Di-hadron correlations reveal a trigger side ridge, possible Mach cones on the away side, vanishing and reappearance of away jets, both wide and normal jet correlations with and without apparent loss of energy. Can this all be explained consistently? Preliminary results of direct γ production in Au+Au appear to indicate a suppression approaching that of π 0 for p T ≈20 GeV/c and a possibly thermal component for 1≤p T ≤ 3 GeV/c. What are the implications? Are fragmentation photons a problem? Regeneration of direct γ by outgoing partons is predicted, leading to negative v 2—is there evidence for or against it? STAR and PHENIX have different observations relevant to the existence of monojets in d+Au collisions. Will new data clarify the situation? When? etc. These and other issues will be discussed with a view to identify which conclusions are firm and where further progress towards real understanding is required.  相似文献   

12.
An internal polarized gas target in conjunction with a beam of polarized protons stored in the IUCF Cooler storage ring has been used to measure analyzing power and spin correlation parameters between 200 MeV and 450 MeV over a wide range of angles. A consistent absolute beam and target polarization calibration was established by ramping the stored protons up and down in energy. The analyzing power A y and the spin correlations A xx , A yy and A xz were measured with transverse beam polarization, while determination of A zz required the development of a longitudinally polarized beam. First experiments on the spin dependence on π0-production have recently been carried out.  相似文献   

13.
The influence of nuclear effects on the transverse momentum (pT) of neutrino-produced hadrons is investigated using the data obtained with the SKAT propane-freon bubble chamber irradiated in the neutrino beam (with E v =3–30 GeV) at the Serpukhov accelerator. It has been observed that the nuclear effects cause an enhancement of 〈p T 2 〉 of hadrons produced in the target fragmentation region at low invariant mass of the hadronic system (2 < W < 4 GeV) and at low energies transferred to the hadrons (2 < ν < 9 GeV). At higher W and ν, no influence of nuclear effects on 〈p T 2 〉 is observed. Measurement results are compared with predictions of a simple model, incorporating secondary intranuclear interactions of hadrons, which qualitatively reproduces the main features of the data.  相似文献   

14.
We have measured the polarization of ∧ and Ξ? hyperons produced inclusively by a Σ? beam of 340 GeV/c momentum in nuclear targets, using samples of 9.5 million ∧ decays and 880000 Ξ? decays. The large statistics allowed a two-dimensional analysis as functions ofx F andp t . The polarization w.r.t. the production normal is mainly positive for ∧ and negative for Ξ?. The positive sign of the ∧ polarization is opposite to predictions. Atp t >1 Gev/c, the ∧ polarization decreases to zero or even negative values, in sharp contrast to the plateau abovep t <1 GeV/c observed in inclusive ∧ production by protons. No such effect is observed for the Ξ? polarization, and its sign is as expected.  相似文献   

15.
The arrangement of an experiment to detect the P?odd and P, T?odd polarized part of the Mössbauer (+3/2– +1/2) gamma transition of a deformed 169Tm nucleus with an energy of 8.4 keV by Compton polarimetry is discussed. Tm 2O3 single crystal with a quadrupolarly split Mössbauer spectrum is proposed as a resonance polarizer. A Be-scatterer-based Compton polarimeter and a synchronously detecting system will be used to measure the P-odd circular polarization PCand P, T-odd linear polarization PL.The expected accuracy of measuring the relative magnitude of the P, T-odd contribution is about 1% of the magnitude of usual weak nucleon–nucleon interaction.  相似文献   

16.
The cross sections for inclusive neutral-pion production in the reactions d + C → π0 + x and d + Cu → π0 + x at a momentum of 4.5 GeV/c per nucleon were measured over the kinematical region specified by the inequalities Θπ≤16° and Eπ≥2 GeV (in the laboratory frame). From the ratio of the cross sections for neutral-pion generation on carbon and copper nuclei, the exponent n in the parametrization Ed3σ/d3pA T n is obtained as a function of the cumulative number X in the range 0.6 ≤ X ≤ 1.8 and as a function of the square of the transverse momentum in the range 0.04 ≤ P t 2 ≤ 0.40 (GeV/c)2. The probabilities of the formation of six-quark configurations in the D, 4He, and 12C nuclei are estimated. The double-differential cross section for the reaction d + C → π0 + x is determined for the first time by using a data sample containing more than 40 000 neutral pions.  相似文献   

17.
Single and double spin asymmetries in the elastic electron-deuteron (e-d ) scattering were investigated. The tensor-deuteron asymmetries T2i(i = 0, 1, 2) and the beam-vector-deuteron asymmetries T e 1i(i = 0, 1) were calculated and compared with the available experimental data. The sensitivity of the results for these spin asymmetries to the deuteron wave function has been investigated. The predicted asymmetries were found to be agree with one another and with experiment. It was found that, the double spin asymmetry T e 10 is much smaller than the T e 11-asymmetry. Therefore, in addition to the single tensor-deuteron asymmetry T20, the doubly beam-vector-deuteron asymmetry T e 11 can be used as an another tool for extracting the deuteron electromagnetic form factors.  相似文献   

18.
Corrections of the α3, α4, and α5 orders are calculated for the Lamb shift of the 1S and 2S energy levels of muonic hydrogen μp and muonic deuterium μd. The nuclear structure effects are taken into account in terms of the charge radii of the proton r p and deuteron r d for one-photon interaction, as well as in terms of the electromagnetic form factors of the proton and deuteron for the case of one-loop amplitudes. The μdp isotope shift for the 1S-2S splitting is found to be equal to 101003.3495 meV, which can be treated as a reliable estimate when conducting the corresponding experiment with an accuracy of 10?6. The fine-structure intervals E(1S)-8E(2S) in muonic hydrogen and muonic deuteron are calculated.  相似文献   

19.
Within a new relativistically invariant approach, the properties of proton clusters that are formed together with Λ and K0 particles in inelastic CC interactions at p=4.2 GeV/c per nucleon are investigated in the space of relative 4-velocities. The observed proton clusters are shown to be characterized by high values of the mean kinetic energy of the protons in the cluster rest frame: 〈T p 〉=100±2 MeV.  相似文献   

20.
The initial stage of a phenomenological analysis of experimental data on the η meson photoproduction off nucleons in the energy range from the threshold to 1.1 GeV is carried out based on a linear nonparametric model. The goal of this stage of the analysis is to obtain statistically reliable information about the partial waves that form the main characteristics of the process. The analysis uses the data of three laboratories about the angular distributions of η-mesons and their Σ and T asymmetries. The results of the analysis of the angular distributions demonstrate the presence of contradictions in the data obtained by different laboratories. The results of the analysis of the energy dependences of the polarization observables Σ and T show that the process regime probably changes in the vicinity of 0.9 GeV, which may be caused by the transition from the region of the S11(1535) and D13(1520) resonances to the region of the D15(1675) and F15(1630) resonances.  相似文献   

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