Observation of polarization in bottomonium production at s**(1/2) = 38.8-GeV

The NuSea collaboration Brown, C.N. ; Awes, T.C. ; Beddo, M.E. ; et al.
Phys.Rev.Lett. 86 (2001) 2529-2532, 2001.
Inspire Record 536629 DOI 10.17182/hepdata.19423

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at sqrt(s)=38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state show no polarization at small xF and pT but significant positive transverse production polarization for either pT > 1.8 GeV/c or for xF > 0.35. The Upsilon(2S+3S) unresolved states show a large transverse production polarization at all values of xF and pT measured. These observations are compared with an NRQCD calculation that predicts a transverse polarization in bottomonium production arising from quark-antiquark fusion and gluon-gluon fusion diagrams.

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Improved measurement of the anti-d/anti-u asymmetry in the nucleon sea.

The NuSea collaboration Towell, R.S. ; McGaughey, P.L. ; Awes, T.C. ; et al.
Phys.Rev.D 64 (2001) 052002, 2001.
Inspire Record 554316 DOI 10.17182/hepdata.22184

Measurements of the ratio of Drell-Yan yields from an 800 \rm{GeV/c} proton beam incident on liquid hydrogen and deuterium targets are reported. Approximately 360,000 Drell-Yan muon pairs remained after all cuts on the data. From these data, the ratio of anti-down ($\bar{d}$) to anti-up ($\bar{u}$) quark distributions in the proton sea is determined over a wide range in Bjorken-$x$. These results confirm previous measurements by E866 and extend them to lower $x$. From these data, $(\bar{d}-\bar{u})$ and $\int(\bar{d}-\bar{u})dx$ are evaluated for $0.015<x<0.35$. These results are compared with parameterizations of various parton distribution functions, models and experimental results from NA51, NMC, and HERMES.

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Measurement of the light antiquark flavor asymmetry in the nucleon sea.

The NuSea collaboration Hawker, E.A. ; Awes, T.C. ; Beddo, M.E. ; et al.
Phys.Rev.Lett. 80 (1998) 3715-3718, 1998.
Inspire Record 468098 DOI 10.17182/hepdata.42153

A precise measurement of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on hydrogen and deuterium targets is reported. Over 140,000 Drell-Yan muon pairs with dimuon mass M_{mu+ mu-} >= 4.5 GeV/c^2 were recorded. From these data, the ratio of anti-down (dbar) to anti-up (ubar) quark distributions in the proton sea is determined over a wide range in Bjorken-x. A strong x dependence is observed in the ratio dbar/ubar, showing substantial enhancement of dbar with respect to ubar for x<0.2. This result is in fair agreement with recent parton distribution parameterizations of the sea. For x>0.2, the observed dbar/ubar ratio is much nearer unity than given by the parameterizations.

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Production of neutral strange particles in muon - nucleon scattering at 490-GeV

The E665 collaboration Adams, M.R. ; Aderholz, M. ; Aïd, S. ; et al.
Z.Phys.C 61 (1994) 539-550, 1994.
Inspire Record 362429 DOI 10.17182/hepdata.42473

The production ofK0, Λ and\(\bar \Lambda \) particles is studied in the E665 muon-nucleon experiment at Fermilab. The average multiplicities and squared transverse momenta are measured as a function ofxF andW2. Most features of the data can be well described by the Lund model. Within this model, the data on the K0/π± ratios and on the averageK0 multiplicity in the forward region favor a strangeness suppression factors/u in the fragmentation process near 0.20. Clear evidence for QCD effects is seen in the average squared transverse momentum ofK0 and Λ particles.

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Measurement of the ratio sigma(n) / sigma(p) in inelastic muon - nucleon scattering at very low x and Q**2

The E665 collaboration Adams, M.R. ; Aïd, S. ; Anthony, P.L. ; et al.
Phys.Lett.B 309 (1993) 477-482, 1993.
Inspire Record 354238 DOI 10.17182/hepdata.28907

We present results on the cross-section ratio for inelastic muon scattering on neutrons and protons as a function of Bjorken chi;. The data extend to χ values two orders of magnitude smaller than in previous measurements, down to 2×10 −5 , for Q 2 >0.01 GeV 2 . The ratio is consistent with unity throughout this new range.

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Real Part of the Proton-Proton Forward Scattering Amplitude from 50-GeV to 400-GeV.

Bartenev, V. ; Carrigan, Richard A. ; Chiang, I-Hung ; et al.
Phys.Rev.Lett. 31 (1973) 1367-1370, 1973.
Inspire Record 81733 DOI 10.17182/hepdata.21379

From measurements of proton-proton elastic scattering at very small momentum transfers where the nuclear and Coulomb amplitudes interfere, we have deduced values of ρ, the ratio of the real to the imaginary forward nuclear amplitude, for energies from 50 to 400 GeV. We find that ρ increases from -0.157 ± 0.012 at 51.5 GeV to +0.039 ± 0.012 at 393 GeV, crossing zero at 280 ± 60 GeV.

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Extraction of the ratio F2(n) / F2(p) from muon - deuteron and muon - proton scattering at small x and Q**2

The E665 collaboration Adams, M.R. ; Aid, S. ; Anthony, P.L. ; et al.
Phys.Rev.Lett. 75 (1995) 1466-1470, 1995.
Inspire Record 393866 DOI 10.17182/hepdata.42379

The ratio of the deuteron to proton structure functions is measured at very small Bjorken x (down to 10–6) and for Q2>0.001 GeV2 from scattering of 470 GeV muons on liquid hydrogen and deuterium targets. The ratio F2n/F2p extracted from these measurements is found to be constant, at a value of 0.935±0.008±0.034, for x<0.01. This result suggests the presence of nuclear shadowing effects in the deuteron. The dependence of the ratio on Q2 is also examined; no significant variation is found.

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Proton and deuteron structure functions in muon scattering at 470-GeV

The E665 collaboration Adams, M.R. ; Aid, S. ; Anthony, P.L. ; et al.
Phys.Rev.D 54 (1996) 3006-3056, 1996.
Inspire Record 416076 DOI 10.17182/hepdata.42347

The proton and deuteron structure functions F2p and F2d are measured in inelastic muon scattering with an average beam energy of 470 GeV. The data were taken at Fermilab experiment E665 during 1991 and 1992 using liquid hydrogen and deuterium targets. The F2 measurements are reported in the range 0.0008<x<0.6 and 0.2<Q2<75 GeV2. These are the first precise measurements of F2 in the low x and Q2 range of the data. In the high x range of the data where they overlap in x and Q2 with the measurements from NMC, the two measurements are in agreement. The E665 data also overlap in x with the DESY HERA data, and there is a smooth connection in Q2 between the two data sets. At high Q2 the E665 measurements are consistent with QCD-evolved leading twist structure function models. The data are qualitatively described by structure function models incorporating the hadronic nature of the photon at low Q2. The Q2 and the W dependence of the data measure the transition in the nature of the photon between a pointlike probe at high Q2 and a hadronic object at low Q2.

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Diffractive production of rho0 (770) mesons in muon - proton interactions at 470-GeV

The E665 collaboration Adams, M.R. ; Aderholz, M. ; Aïd, S. ; et al.
Z.Phys.C 74 (1997) 237-261, 1997.
Inspire Record 441201 DOI 10.17182/hepdata.14214

The diffractive production of ρ0(770 @#@) mesons in muon-proton interactions is studied in the kinematic region 0.15 GeV2< Q2< 20 GeV2 and 20 GeV < ? < 420 GeV. The data were obtained in the Fermilab fixed-target experiment E665 with primary muons of 470 GeV energy. Results are presented on the Q2, x and ? dependence of the cross section, on the shape of the ρ+ρt - mass spectrum, on the slope of the diffraction peak and on the production and decay angular distributions of the ρ0(770). The cross section for diffractive production of ρ0 by virtual photons on protons depends mainly on Q2. At fixed Q2, no significant dependence on x or ? is observed. The extrapolation to Q2 = 0 yields a photoproduction cross section of (10.30 ± 0.33) μb. The slope of the t′ distribution has a value of (7.0 ± 0.2) GeV−2, with a tendency to decrease as Q2 increases. The production and decay angular distributions of the ρ0 depend strongly on Q2 and are consistent with s-channel helicity conservation. The ratio R = σl/σt deduced from the decay angular distributions rises strongly with Q2, passing the value of 1 at Q2≈ 2 GeV2.

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Measurement of Upsilon production for p+p and p+d interactions at 800-GeV

The NuSea collaboration Zhu, L.Y. ; Reimer, Paul E. ; Mueller, B.A. ; et al.
Phys.Rev.Lett. 100 (2008) 062301, 2008.
Inspire Record 763967 DOI 10.17182/hepdata.42715

We report a high statistics measurement of Upsilon production with an 800 GeV/c proton beam on hydrogen and deuterium targets. The dominance of the gluon-gluon fusion process for Upsilon production at this energy implies that the cross section ratio, $\sigma (p + d \to \Upsilon) / 2\sigma (p + p\to \Upsilon)$, is sensitive to the gluon content in the neutron relative to that in the proton. Over the kinematic region 0 < x_F < 0.6, this ratio is found to be consistent with unity, in striking contrast to the behavior of the Drell-Yan cross section ratio $\sigma(p+d)_{DY}/2\sigma(p+p)_{DY}$. This result shows that the gluon distributions in the proton and neutron are very similar. The Upsilon production cross sections are also compared with the p+d and p+Cu cross sections from earlier measurements.

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