Search

Inelastic and elastic J/psi photoproduction on hydrogen are investigated at a mean energy of 105 GeV. The inelastic cross section with E/sub psi/ /E/sub ..gamma../

We have studied muon-produced hadrons from a deuterium target. The structure functions and the charge ratios are reported for neutrons; the transverse momentum and azimuthal distributions are reported for deuterons. The structure function for the neutron is similar to that of the proton. The charge ratio of produced hadrons follows the expectation of a simple spin-1/2 quark model. Transverse-momentum results agree with those at lower energy and are similar to those from hadron--hadron interactions. No azimuthal anisotropy is seen. (AIP)

We have studied D( production mechanisms using data from a photoproduction experiment at the Fermilab Tagged Photon Spectrometer. A large sample of charged D('s was selected via the clean signature of the cascade decay D(..-->..D/sup 0/..pi../sup +/ and subsequently D/sup 0/..-->..K/sup -/..pi../sup +/ or D/sup 0/..-->..K/sup -/..pi../sup +/..pi../sup 0/. The cross section for the process ..gamma..p..-->..(D/sup asterisk+/+anything)p at an average energy of 105 GeV was measured to be 88 +- 32 nb. Only (11 +- 7)% of D('s were found to be consistent with being accompanied solely by a D-bar( or a D-bar; the remaining events contain additional particles. The distribution of the production angle of the D( in the photon-fragmentation-system center of mass is strongly anisotropic and consistent with the form f(theta() = cos/sup 4/theta(. We set a limit on the associated-production-process cross section sigma(..gamma..p..-->..(D-bar/sup asterisk-/+anything)..lambda../sub c/)

Inclusive hadron production in muon-proton inelastic scattering has been measured for ${q}^{2}g0.5$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and $10l\ensuremath{\nu}l135$ GeV. The results are presented in the form of the transverse momentum distribution of charged hadrons and the hadron invariant structure function $F({x}^{\ensuremath{'}})$. Results are given for different regions of ${q}^{2}$ and $s$.

This paper reports measurements of the hadrons produced in the inelastic scattering of 147-GeV muons by protons and deuterons in an experiment carried out at Fermi National Accelerator Laboratory. Both the scattered muon and the hadrons were measured in a large spectrometer. Properties of the hadron spectra are presented for proton, deuteron, and neutron targets and compared with theoretical models and with hadron spectra from related processes. Emphasis is placed on the quark-parton model and the data are found to be in substantial agreement with it. The average transverse momentum of the hadrons with respect to the virtual photon direction shows no dependence on the muon scattering variables. The data display "jet behavior" of the inclusive hadrons comparable to that found in ${e}^{+}{e}^{\ensuremath{-}}$ annihilations.

We have studied the production of $\ensuremath{\rho}$ and $\ensuremath{\varphi}$ mesons from muon scattering on a liquidhydrogen target at 150 and 100 GeV. For the $\ensuremath{\rho}$ we observe a skewed mass distribution which becomes somewhat more normal with increasing ${Q}^{2}$ (the square of the four-momentum transferred from the muon), and an exponential distribution in $t$ (the square of the four-momentum transferred to the target proton) with a slope which is consistent with a slight decrease as ${Q}^{2}$ increases. The dependence of the cross section on ${Q}^{2}$ follows that of the square of the $\ensuremath{\rho}$ propagator with little contribution from longitudinal $\ensuremath{\rho}$ production. The angular distribution of the $\ensuremath{\rho}$ decay confirms the smallness of the contribution from longitudinal $\ensuremath{\rho}$ production at our energies. The cross section when extrapolated to ${Q}^{2}=0$ agrees with that measured in real photoproduction. The decay angular distribution of the $\ensuremath{\rho}$ decay shows that $s$-channel helicity is largely conserved, although we detect a helicity-single-flip contribution at the 10-15% level. Natural-parity exchange in the $t$ channel dominates, and the transverse and longitudinal amplitudes are found to be in phase. These characteristics are consistent with the diffractive nature of the vectordominance model. The $t$ distribution of $\ensuremath{\varphi}$ production is also exponential, although less steep than that for the $\ensuremath{\rho}$. We observe an elastically produced four-pion state at a mass of approximately 1600 MeV. We identify this state with the ${\ensuremath{\rho}}^{\ensuremath{'}}(1600)$, and find it to be produced with a distribution exponential in $t$.

Results are presented from an experiment observing photoproduction of the D( at a mean energy of 105 GeV. Clean signals are seen for the decay D/sup asteriskplus-or-minus/..--> pi../sup + -/D/sup 0/ with the D/sup 0/ decaying into both K/sup - +/..pi../sup + -/ and K/sup - +/..pi../sup + -/..pi../sup 0/. Analysis of the Dalitz plot for the k..pi pi.. mode gives branching fractions for K/sup -/rho/sup +/, K/sup asterisk-/..pi../sup +/, and K-bar /sup asterisk0/..pi../sup 0/ final states.

Results on the nucleon structure function, $\ensuremath{\nu}{W}_{2}$, are presented for $0.2l~{q}^{2}l~50$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and $5l~\ensuremath{\nu}l~130$ GeV. They were obtained by scattering 147-GeV positive muons inelastically from a liquid deuterium target.

Measurements have been made of the inclusive scattering of 96, 147, and 219 GeV muons from hydrogen, and of 147 GeV muons from deuterium. Results are presented for the nucleon structure function F/sub 2/(x,Q/sup 2/) (equivalent..nu..W/sub 2/(x,Q/sup 2/)) for 10 < ..nu.. < 200 GeV and 0.2 < Q/sup 2/ < 80 GeV/sup 2/. The value of F/sub 2/ rises with Q/sup 2/ at small x, and falls with Q/sup 2/ at large x, in agreement with the ideas of quantum chromodynamics. An average value of the ratio sigma/sub L//sigma/sub T/ equivalent R = 0.52 +- 0.35 has been obtained for the region 0.003 < x < 0.10 and 0.4 < Q/sup 2/ < 30 GeV/sup 2/. The values of F/sub 2/ from this experiment have been combined with those from other charged-lepton scattering experiments to determine moments of the structure functions. The variation with Q/sup 2/ of these moments is used to derive values for ..lambda.., taking into account corrections up to second order in ..cap alpha../sub s/. The fit to the data is very good.

Cross sections for diffractive rho muoproduction in hydrogen are presented for 90 GeV

Results on the proton structure function, $\ensuremath{\nu}{W}_{2}$ are presented for $0.3l{q}^{2}l50$ Ge${\mathrm{V}}^{2}$ and $5l\ensuremath{\nu}l130$ GeV. They are compared to earlier data and displayed to demonstrate violations of scaling. Values are reported for the energy-momentum sum rule and for $R\ensuremath{\equiv}\frac{{\ensuremath{\sigma}}_{L}}{{\ensuremath{\sigma}}_{T}}$ over a limited kinematic region.

We have observed coherent production of $\ensuremath{\rho}$ mesons by muon scattering on carbon. The differential cross section falls steeply with increasing $t$ (the square of the four-momentum transferred to the nucleus) and helicity is conserved in the $s$ channel. Dominance by coherent production, as well as the radius of the carbon nucleus and the total $\ensuremath{\rho}$-nucleus cross section derived from our measurements, are consistent with what is observed in other related processes.