Precision measurements of $g_1$ of the proton and the deuteron with 6 GeV electrons

The CLAS collaboration Prok, Y. ; Bosted, P. ; Kvaltine, N. ; et al.
Phys.Rev.C 90 (2014) 025212, 2014.
Inspire Record 1292133 DOI 10.17182/hepdata.64411

The inclusive polarized structure functions of the proton and deuteron, g1p and g1d, were measured with high statistical precision using polarized 6 GeV electrons incident on a polarized ammonia target in Hall B at Jefferson Laboratory. Electrons scattered at lab angles between 18 and 45 degrees were detected using the CEBAF Large Acceptance Spectrometer (CLAS). For the usual DIS kinematics, Q^2>1 GeV^2 and the final-state invariant mass W>2 GeV, the ratio of polarized to unpolarized structure functions g1/F1 is found to be nearly independent of Q^2 at fixed x. Significant resonant structure is apparent at values of W up to 2.3 GeV. In the framework of perturbative QCD, the high-W results can be used to better constrain the polarization of quarks and gluons in the nucleon, as well as high-twist contributions.

4 data tables

Results for G1(P)/F1(P) for the proton in bins of (XB;Q**2), along with average kinematic values and correction factors for each bin. All values are averaged over the event distribution.

Results for G1(DEUT)/F1(DEUT) for the deuteron in bins of (XB;Q**2), along with average kinematic values and correction factors for each bin. All values are averaged over the event distribution.

Results for G1(P)/F1(P) for the proton in bins of (W;Q**2), along with average kinematic values and correction factors for each bin. All values are averaged over the event distribution.

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Inclusive J/psi production in pp collisions at sqrt(s) = 2.76 TeV

The ALICE collaboration Abelev, B. ; Adam, J. ; Adamova, D. ; et al.
Phys.Lett.B 718 (2012) 295-306, 2012.
Inspire Record 1094079 DOI 10.17182/hepdata.62231

The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.

4 data tables

Double differential J/$\psi$ production cross section at $\sqrt{s}=2.76$ TeV. The first uncertainty is statistical, the second one is $p_{\rm T}$-coorelated, the third one is uncorrelated. Polarization-related uncertainties are not included.

The $\sqrt{s}$-dependence of $\langle p_{\rm T}\rangle$ for inclusive J/$\psi$ production (forward rapidity).

the $\sqrt{s}$-dependence of $\langle p_{\rm T}\rangle$ for inclusive J/$\psi$ production (forward rapidity).

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Cross sections and Rosenbluth separations in 1H(e, e'K+)Lambda up to Q2=2.35 GeV2

The Jefferson Lab Hall A collaboration Coman, M. ; Markowitz, P. ; Aniol, K.A. ; et al.
Phys.Rev.C 81 (2010) 052201, 2010.
Inspire Record 837422 DOI 10.17182/hepdata.54197

The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT, cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL.

11 data tables

Measured values of the separated cross section at Q**2 = 2.35 GeV**2 and W = 1.85 GeV.. Errors contain both statistics and systematics.

Measured values of the separated cross section at Q**2 = 1.90 GeV**2.. Errors contain both statistics and systematics.

Measured values of the separated cross section at Q**2 = 2.35 GeV**2.. Errors contain both statistics and systematics.

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Measurements of e+ e- ---> K+ K- eta, K+ K- pi0 and K0(s) K+- pi-+ cross- sections using initial state radiation events

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.
Phys.Rev.D 77 (2008) 092002, 2008.
Inspire Record 765258 DOI 10.17182/hepdata.50372

This paper reports measurements of processes: e+e- -> gamma KsK+pi-, e+e- -> gamma K+K-pi0, e+e- -> gamma phi eta, and e+e- -> gamma phi pi0. The initial state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ~4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BaBar detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KsK+pi- final state, moduli and relative phase of the isoscalar and the isovector components of the e+e- -> K K*(892) cross section are determined. Parameters of phi and rho recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli and phases of the e+e- -> KsK+pi-, K+K-pi0, phi eta final states. The cross section for the OZI-forbidden process e+e- -> phi pi0, and the J/psi branching fractions to KK*(892) and K+K-eta are also measured.

9 data tables

The cross section for E+ E- --> K0S K+ PI- + CC with statistical errors only.

The cross section for E+ E- --> K+ K- PI0 with statistical errors only.

The cross section for E+ E- --> PHI PI0 with statistical errors only.

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The $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$, 2(\pi^+\pi^-)\eta$, $K^+ K^-\pi^+\pi^-\pi^0$ and $K^+ K^-\pi^+\pi^-\eta$ Cross Sections Measured with Initial-State Radiation

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.
Phys.Rev.D 76 (2007) 092005, 2007.
Inspire Record 758568 DOI 10.17182/hepdata.51824

We study the processes $e^+ e^-\to 2(\pi^+\pi^-)\pi^0\gamma$, $2(\pi^+\pi^-)\eta\gamma$, $K^+ K^-\pi^+\pi^-\pi^0\gamma$ and $K^+ K^-\pi^+\pi^-\eta\gamma$ with the hard photon radiated from the initial state. About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective $e^+ e^-$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct \epem measurements, currently available only for the $\eta\pi^+\pi^-$ and $\omega\pi^+\pi^-$ submodes of the $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$ channel. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\to\omega(782)\pi^+\pi^-$ and study the $\omega(1420)$ and $\omega(1650)$ resonances. In the charmonium region, we observe the $J/\psi$ in all these final states and several intermediate states, as well as the $\psi(2S)$ in some modes, and we measure the corresponding branching fractions.

11 data tables

Measured cross section for E+ E- --> 2(PI+ PI-) PI0 with statistical errorsonly.

Measured cross section for E+ E- --> ETA PI+ PI- with statistical errors only.

Measured cross section for E+ E- --> OMEGA PI+ PI- with statistical errors only.

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Measurements of the observed cross sections for $e^+e^- \to$ light hadrons at $\sqrt{s}=$ 3.773 and 3.650 GeV

The BES collaboration Ablikim, M. ; Bai, J.Z. ; Ban, Y. ; et al.
Phys.Lett.B 650 (2007) 111-118, 2007.
Inspire Record 750713 DOI 10.17182/hepdata.26996

Using the data sets of 17.3 pb$^{-1}$ collected at $\sqrt{s}=$ 3.773 GeV and 6.5 pb$^{-1}$ collected at $\sqrt{s}=$ 3.650 GeV with the BESII detector at the BEPC collider, we have measured the observed cross sections for 18 exclusive light hadron final states produced in $e^+e^-$ annihilation at the two energy points.

1 data table

Observed cross sections.


Determination of the Charged Pion Form Factor at Q2=1.60 and 2.45 (GeV/c)2

The Jefferson Lab F(pi)-2 collaboration Horn, T. ; Aniol, K. ; Arrington, J. ; et al.
Phys.Rev.Lett. 97 (2006) 192001, 2006.
Inspire Record 721062 DOI 10.17182/hepdata.31560

The H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F_pi) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F_pi is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative Quantum Chromo-Dynamics prediction.

3 data tables

Separated cross sections at mean Q**2 of 1.60 GeV**2.

Separated cross sections at mean Q**2 of 2.45 GeV**2.

Extracted values of the charged pion form-factor. Errors are the statistical and experimental systematics combined in quadrature.


Decay of the psi(3770) to Light Hadrons

The CLEO collaboration Adams, G.S. ; Anderson, M. ; Cummings, J.P. ; et al.
Phys.Rev.D 73 (2006) 012002, 2006.
Inspire Record 691720 DOI 10.17182/hepdata.52474

We describe a search for psi(3770) decay to two-body non-DDbar final states in e+e- data produced by the CESR collider and analyzed with the CLEO-c detector. Vector-pseudoscalar production of Rho0Pi0, Rho+Pi-, OmegaPi0, PhiPi0, RhoEta, OmegaEta, PhiEta, RhoEtaPrime, OmegaEtaPrime, PhiEtaPrime, Kstar0 K0bar, and Kstar+K- is studied along with that of BOnePi (BOne0Pi0 and BOne+Pi-) and Pi+Pi-Pi0. A statistically significant signal is found for PhiEta, at an excess cross section of (2.4 +- 0.6) pb [Gamma_{PhiEta} (psi(3770)) =(74 +- 16)Mev], and a suggestive suppression of Pi+Pi-Pi0 and RhoPi. We conclude with form factor determinations for OmegaPi0, RhoEta, and RhoEtaPrime.

1 data table

Cross sections at 3.671 and 3.773 GeV.


The Q**2-dependence of the neutron spin structure function g2(n) at low Q**2.

Kramer, K. ; Armstrong, D.S. ; Averett, T.D. ; et al.
Phys.Rev.Lett. 95 (2005) 142002, 2005.
Inspire Record 684137 DOI 10.17182/hepdata.31614

We present the first measurement of the Q^2-dependence of the neutron spin structure function g_2^n at five kinematic points covering 0.57 (GeV/c)^2 <= Q^2 <= 1.34 (GeV/c)^2 at x~0.2. Though the naive quark-parton model predicts g_2=0, non-zero values for g_2 occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses or orbital angular momentum. When scattering from a non-interacting quark, $g_2^n$ can be predicted using next-to-leading order fits to world data for g_1^n. Deviations from this prediction provide an opportunity to examine QCD dynamics in nucleon structure. Our results show a positive deviation from this prediction at lower Q^2, indicating that contributions such as quark-gluon interactions may be important. Precision data obtained for g_1^n are consistent with next-to-leading order fits to world data.

1 data table

Measured values of G1N ang G2N.


Precision measurement of the neutron spin asymmetries and spin-dependent structure functions in the valence quark region.

The Jefferson Lab Hall A collaboration Zheng, X. ; Aniol, K. ; Armstrong, D.S. ; et al.
Phys.Rev.C 70 (2004) 065207, 2004.
Inspire Record 650244 DOI 10.17182/hepdata.31726

We report on measurements of the neutron spin asymmetries $A_{1,2}^n$ and polarized structure functions $g_{1,2}^n$ at three kinematics in the deep inelastic region, with $x=0.33$, 0.47 and 0.60 and $Q^2=2.7$, 3.5 and 4.8 (GeV/c)$^2$, respectively. These measurements were performed using a 5.7 GeV longitudinally-polarized electron beam and a polarized $^3$He target. The results for $A_1^n$ and $g_1^n$ at $x=0.33$ are consistent with previous world data and, at the two higher $x$ points, have improved the precision of the world data by about an order of magnitude. The new $A_1^n$ data show a zero crossing around $x=0.47$ and the value at $x=0.60$ is significantly positive. These results agree with a next-to-leading order QCD analysis of previous world data. The trend of data at high $x$ agrees with constituent quark model predictions but disagrees with that from leading-order perturbative QCD (pQCD) assuming hadron helicity conservation. Results for $A_2^n$ and $g_2^n$ have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment $d_2^n$ was evaluated and the new result has improved the precision of this quantity by about a factor of two. When combined with the world proton data, polarized quark distribution functions were extracted from the new $g_1^n/F_1^n$ values based on the quark parton model. While results for $\Delta u/u$ agree well with predictions from various models, results for $\Delta d/d$ disagree with the leading-order pQCD prediction when hadron helicity conservation is imposed.

6 data tables

Measurements of the HE3 asymmetries.

Measurements of the HE3 spin structure functions.

Measurements of the HE3 spin structure functions.

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