Baker, W.F.
Max results
Sort by Reverse order

Showing 10 of 1117 results

Date

rivet Analysis
Measurement of the eta and eta' transition form factors at q**2 = 112-GeV**2.

The BaBar collaboration Aubert, Bernard ; Barate, R. ; Bona, M. ; et al.
Phys.Rev.D 74 (2006) 012002, 2006.
Inspire Record 716277 DOI 10.17182/hepdata.22085

We report a study of the processes e+e- -> eta gamma and e+e- -> etaprime gamma at a center-of-mass energy of 10.58 GeV, using a 232 fb^-1 data sample collected with the BABAR detector at the PEP-II collider at SLAC. We observe 20+6-5 eta gamma and 50+8-7 etaprime gamma events over small backgrounds, and measure the cross sections sigma(e+e- -> eta gamma) =4.5+1.2-1.1(stat)+-0.3(sys) fb and sigma(e+e- -> etaprime gamma)=5.4+-0.8(stat)+-0.3(sys) fb. The corresponding transition form factors at q^2 = 112 GeV^2 are q^2|F_eta(q^2)|=0.229+-0.030+-0.008 GeV, and q^2|F_etaprime(q^2)|=0.251+-0.019+-0.008 GeV, respectively.

3 data tables
Table 1

Measured cross sections.

Table 2

Undressed cross sections calculated by applying a 7.5 +- 0.2 PCT correction for vacuum polarization.

Table 3

Transition form factors at Q**2 = 112 GeV**2.


rivet Analysis
The e+ e- ---> 3(pi+ pi-), 2(pi+ pi- pi0) and K+ K- 2(pi+ pi-) cross sections at center-of-mass energies from production threshold to 4.5-GeV measured with initial-state radiation

The BaBar collaboration Aubert, Bernard ; Barate, R. ; Boutigny, D. ; et al.
Phys.Rev.D 73 (2006) 052003, 2006.
Inspire Record 709730 DOI 10.17182/hepdata.41843

We study the processes e+ e- --> 3(pi+pi-)gamma, 2(pi+pi-pi0)gamma and K+ K- 2(pi+pi-)gamma, with the photon radiated from the initial state. About 20,000, 33,000 and 4,000 fully reconstructed events, respectively, have been 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 these data can be compared with the corresponding direct e+e- measurements. From the 3(pi+pi-), 2(pi+pi-pi0) and K+ K- 2(pi+pi-) mass spectra, the cross sections for the processes e+ e- --> 3(pi+pi-), e+ e- --> 2(pi+pi-pi0) and e+ e- --> K+ K- 2(pi+pi-) are measured for center-of-mass energies from production threshold to 4.5 GeV. The uncertainty in the cross section measurement is typically 6-15%. We observe the J/psi in all these final states and measure the corresponding branching fractions.

3 data tables
Table 1

The cross section for E+ E- --> 3PI+ 3PI- as measured with the ISR data. Errors are statistical only.

Table 2

The cross section for E+ E- --> 2PI+ 2PI- 2PI0 as measured with the ISR data. Errors are statistical only.

Table 3

The cross section for E+ E- --> K+ K- 2PI+ 2PI- as measured with the ISR data. Errors are statistical only.


rivet Analysis
A Study of e+ e- ---> p anti-p using initial state radiation with BABAR

The BaBar collaboration Aubert, Bernard ; Barate, R. ; Boutigny, D. ; et al.
Phys.Rev.D 73 (2006) 012005, 2006.
Inspire Record 700020 DOI 10.17182/hepdata.41831

The e+e- -> p anti-p cross section is determined over a range of p anti-p masses, from threshold to 4.5 GeV/c^2, by studying the e+e- -> p anti-p gamma process. The data set corresponds to an integrated luminosity of 232 fb^-1, collected with the BABAR detector at the PEP-II storage ring, at an e+e- center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, is measured for p anti-p masses below 3 GeV/c^2: its value is found to be significantly larger than 1 for masses up to 2.2 GeV/c^2. We also measure J/psi -> p anti-p and psi(2S) -> p anti-p branching fractions and set an upper limit on Y(4260) -> p anti-p production and decay.

2 data tables
Table 1

The cross section and effective form factor for E+ E- --> PBAR P.

Table 2

The cross section and effective form factor for E+ E- --> PBAR P.


rivet Analysis
Measurement of the cross section for e+ e- --> p anti-p at center-of-mass energies from 2.0-GeV to 3.07-GeV.

The BES collaboration Ablikim, M. ; Bai, J.Z. ; Ban, Y. ; et al.
Phys.Lett.B 630 (2005) 14-20, 2005.
Inspire Record 685906 DOI 10.17182/hepdata.41880

Cross sections for e^+e^- -> ppbar have been measured at 10 center-of-mass energies from 2.0 to 3.07 GeV by the BESII experiment at the BEPC, and proton electromagnetic form factors in the time-like region have been determined.

1 data table
Table 1

Cross section and proton form factor measurements. The cross section quoted is the lowest order cross section corrected for initial and final state radiation and coulomb effects.


Measurement of direct photon production at Tevatron fixed target energies.

The Fermilab E706 collaboration Apanasevich, L. ; Bacigalupi, J. ; Baker, W. ; et al.
Phys.Rev.D 70 (2004) 092009, 2004.
Inspire Record 653834 DOI 10.17182/hepdata.42777

Measurements of the production of high transverse momentum direct photons by a 515 GeV/c piminus beam and 530 and 800 GeV/c proton beams in interactions with beryllium and hydrogen targets are presented. The data span the kinematic ranges of 3.5 < p_T < 12 GeV/c in transverse momentum and 1.5 units in rapidity. The inclusive direct-photon cross sections are compared with next-to-leading-order perturbative QCD calculations and expectations based on a phenomenological parton-k_T model.

18 data tables
Table 1

Invariant cross sections per nucleon for P BE collisions at 800 GeV.

Table 2

Invariant cross sections per nucleon for P BE collisions at 530 GeV.

Table 3

Invariant cross sections per nucleon for PI- BE collisions at 515 GeV.

More…

Photon electroproduction from hydrogen at backward angles and momentum transfer squared of Q**2 = 1.0-GeV**2.

The JLab Hall A collaboration Laveissiere, G. ; Degrande, N. ; Jaminion, S. ; et al.
JLAB-PHY-04-34, 2004.
Inspire Record 652965 DOI 10.17182/hepdata.38623

We have made the first measurements of the virtual Compton scattering process via the e p -> e p gamma exclusive reaction at Q**2 = 1 GeV**2 in the nucleon resonance region. The cross section is obtained at center of mass (CM) backward angle, theta_gamma_gamma*, in a range of total (gamma* p) CM energy W from the proton mass up to W = 1.91 GeV. The data show resonant structures in the first and second resonance regions, and are well reproduced at higher W by the Bethe-Heitler+Born cross section, including t-channel pi0-exchange. At high W, our data, together with existing real photon data, show a striking Q**2 independence. Our measurement of the ratio of H(e,e'p)gamma to H(e,e'p)pi0 cross sections is presented and compared to model predictions.

18 data tables
Table 1

Cross section for the reaction E P --> E P GAMMA at a polar angle given by COS(THETA) = -0.975 and azimuthal angle PHI = 15 degrees both in the centre-of-mass frame of the GAMMA* P --> GAMMA* P reaction.

Table 2

Cross section for the reaction E P --> E P GAMMA at a polar angle given by COS(THETA) = -0.975 and azimuthal angle PHI = 45 degrees both in the centre-of-mass frame of the GAMMA* P --> GAMMA* P reaction.

Table 3

Cross section for the reaction E P --> E P GAMMA at a polar angle given by COS(THETA) = -0.975 and azimuthal angle PHI = 75 degrees both in the centre-of-mass frame of the GAMMA* P --> GAMMA* P reaction.

More…

Near threshold electroproduction of the omega meson at Q**2 approx. 0.5-GeV**2.

The Jefferson Laboratory E91-016 collaboration Ambrozewicz, P. ; Mitchell, J. ; Dunne, J. ; et al.
Phys.Rev.C 70 (2004) 035203, 2004.
Inspire Record 645605 DOI 10.17182/hepdata.31643

Electroproduction of the omega meson was investigated in the p(e,e'p)omega reaction. The measurement was performed at a 4-momentum transfer Q2 ~ 0.5 GeV2. Angular distributions of the virtual photon-proton center-of-momentum cross sections have been extracted over the full angular range. These distributions exhibit a strong enhancement over t-channel parity exchange processes in the backward direction. According to a newly developed electroproduction model, this enhancement provides significant evidence of resonance formation in the gamma* p -> omega p reaction channel.

2 data tables
Table 1

Differential cross section for an average W of 1.75 GeV.

Table 2

Differential cross section for an average W of 1.79 GeV.


Measurements of electron proton elastic cross sections for 0.4-(GeV/c)**2 < Q**2 < 5.5-(GeV/c)**2.

The E94110 collaboration Christy, M.E. ; Ahmidouch, A. ; Armstrong, C.S. ; et al.
Phys.Rev.C 70 (2004) 015206, 2004.
Inspire Record 643262 DOI 10.17182/hepdata.31763

We report on precision measurements of the elastic cross section for electron-proton scattering performed in Hall C at Jefferson Lab. The measurements were made at 28 unique kinematic settings covering a range in momentum transfer of 0.4 $<$ $Q^2$ $<$ 5.5 $(\rm GeV/c)^2$. These measurements represent a significant contribution to the world's cross section data set in the $Q^2$ range where a large discrepancy currently exists between the ratio of electric to magnetic proton form factors extracted from previous cross section measurements and that recently measured via polarization transfer in Hall A at Jefferson Lab.

7 data tables
Table 1

Measured values of the electron-proton elastic cross section for beam energy 1.148 GeV.

Table 2

Measured values of the electron-proton elastic cross section for beam energy 1.882 GeV.

Table 3

Measured values of the electron-proton elastic cross section for beam energy 2.235 GeV.

More…

Backward electroproduction of pi0 mesons on protons in the region of nucleon resonances at four momentum transfer squared Q**2 = 1.0-GeV**2.

The JLab Hall A collaboration Laveissiere, G. ; Degrande, N. ; Jaminion, S. ; et al.
Phys.Rev.C 69 (2004) 045203, 2004.
Inspire Record 625669 DOI 10.17182/hepdata.25226

Exclusive electroproduction of pi0 mesons on protons in the backward hemisphere has been studied at Q**2 = 1.0 GeV**2 by detecting protons in the forward direction in coincidence with scattered electrons from the 4 GeV electron beam in Jefferson Lab's Hall A. The data span the range of the total (gamma* p) center-of-mass energy W from the pion production threshold to W = 2.0 GeV. The differential cross sections sigma_T+epsilon*sigma_L, sigma_TL, and sigma_TT were separated from the azimuthal distribution and are presented together with the MAID and SAID parametrizations.

12 data tables
Table 1

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.975.

Table 2

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.925.

Table 3

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.875.

More…

Production of pi0 and eta mesons at large transverse momenta in pi- p and pi- Be interactions at 515-GeV/c.

The Fermilab E706 collaboration Apanasevich, L. ; Bacigalupi, J. ; Baker, W. ; et al.
Phys.Rev.D 69 (2004) 032003, 2004.
Inspire Record 625447 DOI 10.17182/hepdata.42836

We present results on the production of high transverse momentum pizero and eta mesons in pi-p and pi-Be interactions at 515 GeV/c. The data span the kinematic ranges 1 < p_T < 11 GeV/c in transverse momentum and -0.75 < y < 0.75 in rapidity. The inclusive pizero cross sections are compared with next-to-leading order QCD calculations and to expectations based on a phenomenological parton-k_T model.

19 data tables
Table 1

Invariant differential cross section per nucleon for inclusive PI0 production in PI- BE collisions at 515 GeV averaged over the cm rapidity interval -0.75 to 0.75.

Table 2

Invariant differential cross section for inclusive PI0 production in PI- P collisions at 515 GeV averaged over the cm rapidity interval -0.75 to 0.75.

Table 3

The averaged invariant differential cross section per nucleon as a functionof rapidity in the PT intervals 1.00 to 1.50 and 1.50 to 2.00 GeV for PI0 produ ction in PI- BE interactions at 515 GeV.

More…