Measurement of Spin Density Matrix Elements in $\Lambda(1520)$ Photoproduction at 8.2-8.8 GeV

The GlueX collaboration Adhikari, S. ; Akondi, C.S. ; Albrecht, M. ; et al.
Phys.Rev.C 105 (2022) 035201, 2022.
Inspire Record 1892395 DOI 10.17182/hepdata.132920

We report on the measurement of spin density matrix elements of the $\Lambda(1520)$ in the photoproduction reaction $\gamma p\rightarrow \Lambda(1520)K^+$, via its subsequent decay to $K^{-}p$. The measurement was performed as part of the GlueX experimental program in Hall D at Jefferson Lab using a linearly polarized photon beam with $E_\gamma =$ 8.2-8.8 GeV. These are the first such measurements in this photon energy range. Results are presented in bins of momentum transfer squared, $-(t-t_\text{0})$. We compare the results with a Reggeon exchange model and determine that natural exchange amplitudes are dominant in $\Lambda(1520)$ photoproduction.

10 data tables

Numerical results for all presented SDMEs. The first uncertainty is statistical, the second systematic

Numerical results for all presented natural and unnatural combinations, and covariances between $\rho^1_{11}$ and $\rho^1_{33}$. The first uncertainty is statistical, the second systematic

This table contains thinned out samples of the Markov chains used in the parameter estimation of the SDME measurements for $-(t-t_\text{0}) = 0.197\pm0.069~\text{GeV}^2/c^2$, reported in the main article. One in about 250 steps in the chain, which results in 200 different sets of SDMEs, is provided. These values should be used instead of bootstrapping of the results, in order to estimate uncertainties of physics models fitted to this data. To assess how the uncertainties propagate to the model uncertainties, one should evaluate the model under scrutiny for each of the 200 different sets of SDMEs. Plotting all resulting lines in a single plot will create bands which reflect the influence of the uncertainties in the data on the model. This method has the great advantage that all correlations are accurately taken into account.

More…

Bubble Chamber Study of Photoproduction by 2.8-GeV and 4.7-GeV Polarized Photons. 1. Cross-Section Determinations and Production of rho0 and Delta++ in the Reaction gamma p --> p pi+ pi-

Ballam, Joseph ; Chadwick, G.B. ; Gearhart, R. ; et al.
Phys.Rev.D 5 (1972) 545, 1972.
Inspire Record 67165 DOI 10.17182/hepdata.3635

Photoproduction is studied at 2.8 and 4.7 GeV using a linearly polarized monoenergetic photon beam in a hydrogen bubble chamber. We discuss the experimental procedure, the determination of channel cross sections, and the analysis of the channel γp→pπ+π−. A model-independent analysis of the ρ0-decay angular distribution allows us to measure nine independent density-matrix elements. From these we find that the reaction γp→pρ0 proceeds almost completely through natural parity exchange for squared momentum transfers |t|<1 GeV2 and that the ρ production mechanism is consistent with s-channel c.m. helicity conservation for |t|<0.4 GeV2. A cross section for the production of π+π− pairs in the s-channel c.m. helicity-conserving p-wave state is determined. The ρ mass shape is studied as a function of momentum transfer and is found to be inconsistent with a t-independent Ross-Stodolsky factor. Using a t-dependent parametrization of the ρ0 mass shape we derive a phenomenological ρ0 cross section. We compare our phenomenological ρ0 cross section with other experiments and find good agreement for 0.05<|t|<1 GeV2. We discuss the discrepancies in the various determinations of the forward differential cross section. We study models for ρ0 photoproduction and find that the Söding model best describes the data. Using the Söding model we determine a ρ0 cross section. We determine cross sections and nine density-matrix elements for γp→Δ++π−. The parity asymmetry for Δ++ production is incompatible with simple one-pion exchange. We compare Δ++ production with models.

20 data tables

FROM QUOTED TOPOLOGICAL CROSS SECTIONS. 1.44 GEV CROSS SECTION PUBLISHED PREVIOUSLY.

No description provided.

NO TMIN CORRECTION HAS BEEN MADE.

More…

Exclusive electroproduction of J/psi mesons at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Krakauer, D. ; et al.
Nucl.Phys.B 695 (2004) 3-37, 2004.
Inspire Record 647777 DOI 10.17182/hepdata.46277

The exclusive electroproduction of J/psi mesons, ep->epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15<Q^2<0.8 GeV^2 and 2<Q^2<100 GeV^2 using integrated luminosities of 69 pb^-1 and 83 pb^-1, respectively.The photon-proton centre-of-mass energy was in the range 30<W<220 GeV and the squared four-momentum transfer at the proton vertex |t|<1.The cross sections and decay angular distributions are presented as functions of Q^2, W and t. The effective parameters of the Pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma_L/sigma_T, grows with Q^2, whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.

20 data tables

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 0.15 to 0.18 GeV**2.

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 2 to 5 GeV**2.

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 5 to 10 GeV**2.

More…

Electroproduction of $\phi(1020)$ mesons at $1.4\leq Q^2\leq$ 3.8 GeV$^2$ measured with the CLAS spectrometer

The CLAS collaboration Santoro, J.P. ; Smith, E.S. ; Garc con, M. ; et al.
Phys.Rev.C 78 (2008) 025210, 2008.
Inspire Record 781974 DOI 10.17182/hepdata.50913

Electroproduction of exclusive $\phi$ vector mesons has been studied with the CLAS detector in the kinematical range $1.6\leq Q^2\leq 3.8$ GeV$^{2}$, $0.0\leq t^{\prime}\leq 3.6$ GeV$^{2}$, and $2.0\leq W\leq 3.0$ GeV. The scaling exponent for the total cross section as $1/(Q^2+M_{\phi}^2)^n$ was determined to be $n=2.49\pm 0.33$. The slope of the four-momentum transfer $t'$ distribution is $b_{\phi}=0.98 \pm 0.17$ GeV$^{-2}$. The data are consistent with the assumption of s-channel helicity conservation (SCHC). Under this assumption, we determine the ratio of longitudinal to transverse cross sections to be $R=0.86 \pm 0.24$. A 2-gluon exchange model is able to reproduce the main features of the data.

5 data tables

Axis error includes +- 18.6/18.6 contribution.

Axis error includes +- 18.6/18.6 contribution.

Axis error includes +- 18.6/18.6 contribution.

More…

Exclusive rho^0 production in deep inelastic scattering at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
PMC Phys.A 1 (2007) 6, 2007.
Inspire Record 757991 DOI 10.17182/hepdata.54963

Exclusive rho^0 electroproduction at HERA has been studied with the ZEUS detector using 120 pb^{-1} of integrated luminosity collected during 1996-2000. The analysis was carried out in the kinematic range of photon virtuality 2 < Q^2 < 160 GeV$^2, and gamma^* p centre-of-mass energy 32 < W < 180 GeV. The results include the Q^2 and W dependence of the gamma^* p --> rho^0 p cross section and the distribution of the squared-four-momentum transfer to the proton. The helicity analysis of the decay-matrix elements of the rho^0 was used to study the ratio of the gamma^* p cross section for longitudinal and transverse photon as a function of Q^2 and W. Finally, an effective Pomeron trajectory was extracted. The results are compared to various theoretical predictions.

30 data tables

Measurement of the spin density matrix element r_04_00 as a function of Q**2.

Measurement of the spin density matrix element RE(r_04_10) as a function of Q**2.

Measurement of the spin density matrix element r_04_1-1 as a function of Q**2.

More…

Elastic J/psi production at HERA.

The H1 collaboration Aktas, A. ; Andreev, V. ; Anthonis, T. ; et al.
Eur.Phys.J.C 46 (2006) 585-603, 2006.
Inspire Record 694372 DOI 10.17182/hepdata.46134

Cross sections for elastic production of J/Psi mesons in photoproduction and electroproduction are measured in electron proton collisions at HERA using an integrated luminosity of 55 pb^{-1}. Results are presented for photon virtualities Q^2 up to 80 GeV^2. The dependence on the photon-proton centre of mass energy W_{gamma p} is analysed in the range 40 < \Wgp < 305 GeV in photoproduction and 40 < \Wgp < 160 GeV in electroproduction. The \Wgp dependences of the cross sections do not change significantly with Q^2 and can be described by models based on perturbative QCD. Within such models, the data show a high sensitivity to the gluon density of the proton in the domain of low Bjorken x and low Q^2. Differential cross sections d\sigma/dt, where t is the squared four-momentum transfer at the proton vertex, are measured in the range |t|<1.2 GeV^2 as functions of \Wgp and Q^2. Effective Pomeron trajectories are determined for photoproduction and electroproduction. The J/Psi production and decay angular distributions are consistent with s-channel helicity conservation. The ratio of the cross sections for longitudinally and transversely polarised photons is measured as a function of Q^2 and is found to be described by perturbative QCD based models.

19 data tables

Cross section for elastic J/PSI photoproduction in Q**2 bins for W = 90 GeV and ABS(T) < 1.2 GeV**2.

Cross section for elastic J/PSI photoproduction in W bins for ABS(T) < 1.2 GeV**2 and Q**2 < 1 GeV**2.. There are two cross sections for the 205 to 235 GeV bin due to overlapping data sets. The mean is 151 +- 8 (DSYS=20) nb.

Cross section for elastic J/PSI photoproduction as a function of W in Q**2 bins for ABS(T) < 1.2 GeV**2.

More…

Deeply virtual and exclusive electroproduction of omega mesons.

The CLAS collaboration Morand, L. ; Dore, D. ; Garcon, M. ; et al.
Eur.Phys.J.A 24 (2005) 445-458, 2005.
Inspire Record 681604 DOI 10.17182/hepdata.43499

The exclusive omega electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q2) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross sections were measured up to large values of the four-momentum transfer (-t < 2.7 GeV2) to the proton. The contributions of the interference terms sigma_TT and sigma_TL to the cross sections, as well as an analysis of the omega spin density matrix, indicate that helicity is not conserved in this process. The t-channel pi0 exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction gamma* p -> omega p, even for Q2 as large as 5 GeV2. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross sections is nearly Q2-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit.

85 data tables

Total cross sections and interference terms (TT and TL).

Differential cross sections DSIG/DT for Q**2 = 1.725 GeV**2 and W = 2.77 GeV.

Differential cross sections DSIG/DT for Q**2 = 1.752 GeV**2 and W = 2.48 GeV.

More…

Diffractive photoproduction of J / psi mesons with large momentum transfer at HERA

The H1 collaboration Aktas, A. ; Andreev, V. ; Anthonis, T. ; et al.
Phys.Lett.B 568 (2003) 205-218, 2003.
Inspire Record 620283 DOI 10.17182/hepdata.46431

The diffractive photoproduction of J/psi mesons is measured with the H1 detector at the ep collider HERA using an integrated luminosity of 78 pb^-1. The differential cross section d sigma(gamma p -> J/psi Y) / d t is studied in the range 2 < |t| < 30 GeV^2, where t is the square of the four-momentum transferred at the proton vertex. The cross section is also presented as a function of the photon-proton centre-of-mass energy W in three t intervals, spanning the range 50 < W < 200 GeV. A fast rise of the cross section with W is observed for each t range and the slope for the effective linear Pomeron trajectory is measured to be alpha^\prime= -0.0135 \pm 0.0074 (stat.) \pm 0.0051 (syst.) GeV^-2. The measurements are compared with perturbative QCD models based on BFKL and DGLAP evolution. The data are found to be compatible with s-channel helicity conservation.

6 data tables

The differential photoproduction cross section DSIG/DT for diffractive J/PSI production.

The J/PSI photoproduction cross section as a function of W for the ABS(T) range 2 to 5 GeV**2.

The J/PSI photoproduction cross section as a function of W for the ABS(T) range 5 to 10 GeV**2.

More…

Measurement of the spin-density matrix elements in exclusive electroproduction of rho0 mesons at HERA.

The ZEUS collaboration Breitweg, J. ; Chekanov, S. ; Derrick, M. ; et al.
Eur.Phys.J.C 12 (2000) 393-410, 2000.
Inspire Record 505172 DOI 10.17182/hepdata.24209

Exclusive electroproduction of rho^0 mesons has been measured using the ZEUS detector at HERA in two Q^2 ranges, 0.25<Q^2<0.85 GeV^2 and 3<Q^2<30 GeV^2. The low-Q^2 data span the range 20<W<90 GeV; the high-Q^2 data cover the 40<W<120 GeV interval. Both samples extend up to four-momentum transfers of |t|=0.6 GeV^2. The distribution in the azimuthal angle between the positron scattering plane and the rho^0 production plane shows a small but significant violation of s-channel helicity conservation, corresponding to the production of longitudinally polarised (i.e. helicity zero) rho^0 mesons from transverse photons. Measurements of the 15 combinations of spin-density matrix elements which completely define the angular distributions are presented and discussed.

8 data tables

The spin-density matrix elements obtained from the BPC low Q**2 data set.

The spin-density matrix elements obtained from the DIS high Q**2 data set.

The spin-density matrix elements obtained from the low Q**2 BPC data set in two W intervals.

More…

A measurement of the t dependence of the helicity structure of diffractive rho meson electroproduction at HERA.

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Phys.Lett.B 539 (2002) 25-39, 2002.
Inspire Record 584099 DOI 10.17182/hepdata.46666

The helicity structure of the diffractive electroproduction of rho mesons, e + p -> e + rho + Y, is studied in a previously unexplored region of large four-momentum transfer squared at the proton vertex, t: 0 < t' < 3 GeV^2, where t' = |t| - |t|_min. The data used are collected with the H1 detector at HERA in the kinematic domain 2.5 < Q^2 < 60 GeV^2, 40 < W < 120 GeV. No t dependence of the r^04_00 spin density matrix element is found. A significant t dependent helicity non-conservation from the virtual photon to the rho meson is observed for the spin density matrix element combinations r^5_00+2r^5_11 and r^1_00+2r^1_11. These t dependences are consistently described by a perturbative QCD model based on the exchange of two gluons.

1 data table

Measurements of the combinations of spin density matrices as a function of TP = |T| - |Tmin|, where |Tmin| is the minimal values of |T| kinematically required for the vector meson and the system X to aquire their effective mass through longitudinal momentum transfer.


Measurement of proton dissociative diffractive photoproduction of vector mesons at large momentum transfer at HERA.

The ZEUS collaboration Chekanov, S. ; Krakauer, D. ; Magill, S. ; et al.
Eur.Phys.J.C 26 (2003) 389-409, 2003.
Inspire Record 587202 DOI 10.17182/hepdata.46584

Diffractive photoproduction of vector mesons, gamma p --> V Y, where Y is a proton-dissociative system, has been measured in ep interactions with the ZEUS detector at HERA using an integrated luminosity of 25 pb^-1. The differential cross section, ds/dt, is presented for -t<12 GeV^2, where t is the square of the four-momentum transferred to the vector meson. The data span the range in photon-proton centre-of-mass energy, W, from 80 GeV to 120 GeV. The t distributions are well fit by a power law, ds/dt ~ (-t)^{-n}. The slope of the Pomeron trajectory, measured from the W dependence of the rho^0 and phi cross sections in bins of t, is consistent with zero. The ratios ds_(gamma p --> phi Y)/dt to ds_(gamma p --> rho^0 Y)/dt and ds_(gamma p --> J/psi Y)/dt to ds_(gamma p --> rho^0 Y)/dt increase with increasing -t. Decay-angle analyses for rho^0, phi and J/psi mesons have been carried out. For the rho^0 and phi mesons, contributions from single and double helicity flip are observed. The results are compared to expectations of theoretical models.

8 data tables

Differential cross section for RHO0 production. The second DSYS error is due to the modelling of the proton-dissociation process.

Differential cross section for PHI production. The second DSYS error is due to the modelling of the proton-dissociation process.

Differential cross section for J/PSI production. The second DSYS error is due to the modelling of the proton-dissociation process.

More…

Exclusive photoproduction of J/psi mesons at HERA.

The ZEUS collaboration Chekanov, S. ; Krakauer, D. ; Magill, S. ; et al.
Eur.Phys.J.C 24 (2002) 345-360, 2002.
Inspire Record 582237 DOI 10.17182/hepdata.46713

The exclusive photoproduction of J/psi mesons, gamma p->J/psi p, has been studied in ep collisions with the ZEUS detector at HERA, in the kinematic range 20<W<290 GeV, where W is the photon-proton centre-of-mass energy. The J/psi mesons were reconstructed in the muon and the electron decay channels using integrated luminosities of 38 pb^-1 and 55 pb^-1, respectively. The helicity structure of J/psi production shows that the hypothesis of s-channel helicity conservation is satisfied at the two standard-deviation level. The total cross section and the differential cross-section dsigma/dt, where t is the squared four-momentum transfer at the proton vertex, are presented as a function of W, for |t|<1.8 GeV^2. The t distribution exhibits an exponential shape with a slope parameter increasing logarithmically with W with a value b=4.15 \pm 0.05 (stat.)^{+0.30}_{-0.18} (syst.) GeV^-2 at W=90 GeV. The effective parameters of the Pomeron trajectory are alphapom(0) = 1.200 \pm 0.009(stat.)^{+0.004}_{-0.010}(syst.) and alphappom= 0.115 \pm 0.018(stat.)^{+0.008}_{-0.015}(syst.) GeV^-2.

12 data tables

The total exclusive J/PSI photoproduction cross section, the differential cross section extrapolated to t=0 and the slope parameter of the exponential t dependence as afunction of W, the photon-proton c.m. energy, for data from J/PSI muon decay.

The total exclusive J/PSI photoproduction cross section as a function of W,the photon-proton c.m. energy, for data from J/PSI electron decays.

The differential cross section extrapolated to t=0 and the slope parameter of the exponential t dependence for exclusive J/PSI photoproduction as a function of W, the photon-proton c.m. energy for data from J/PSI electron decays.

More…

Measurement of elastic electroproduction of Phi mesons at HERA.

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Phys.Lett.B 483 (2000) 360-372, 2000.
Inspire Record 526887 DOI 10.17182/hepdata.47016

The elastic electroproduction of phi mesons is studied at HERA with the H1 detector for photon virtualities 1 < Q^2 < 15 GeV^2 and hadronic centre of mass energies 40 < W < 130 GeV. The Q^2 and t dependences of the cross section are extracted (t being the square of the four-momentum transfer to the target proton). When plotted as function of (Q^2 + M_V^2) and scaled by the appropriate SU(5) quark charge factor, the phi meson cross section agrees within errors with the cross sections of the vector mesons V = rho, omega and J/psi. A detailed analysis is performed of the phi meson polarisation state and the ratio of the production cross sections for longitudinally and transversely polarised phi mesons is determined. A small but significant violation of s-channel helicity conservation (SCHC) is observed.

7 data tables

The measured ratio of PHI to RHO0 production.

The cross section for elastic PHI meson electro-production calculated by multiplying the PHI/RHO0 cross section ratio by the RHO0 cross section accurately measured in the earlier H1 publication (EPJ C13,371).

The corrected T distribution of elastic PHI meson production for W around 75 GeV and Q2 in the range 2.5 to 15 GeV**2 (mean = 4.8 GeV**2). Statistical error only.

More…

Measurement of diffractive photoproduction of vector mesons at large momentum transfer at HERA.

The ZEUS collaboration Breitweg, J. ; Chekanov, S. ; Derrick, M. ; et al.
Eur.Phys.J.C 14 (2000) 213-238, 2000.
Inspire Record 508770 DOI 10.17182/hepdata.43866

Elastic and proton-dissociative photoproduction of $\rho^0$, $\phi$ and $J/\psi$ vector mesons ($\gamma p\to Vp$, $\gamma p\to VN$, respectively) have been measured in e^+p interactions at HERA up to -t=3 GeV$^2$, where t is the four-momentum transfer squared at the photon-vector meson vertex. The analysis is based on a data sample in which photoproduction reactions were tagged by detection of the scattered positron in a special-purpose calorimeter. This limits the photon virtuality, Q^2, to values less than 0.01 GeV$^2$, and selects a $\gamma p$ average center-of-mass energy of <W> = 94 GeV. Results for the differential cross sections, d$\sigma$/d$t$, for $\rho^0$, $\phi$ and $J/\psi$ mesons are presented and compared to the results of recent QCD calculations. Results are also presented for the t-dependence of the pion-pair invariant-mass distribution in the $\rho^0$ mass region and of the spin-density matrix elements determined from the decay-angle distributions. The Pomeron trajectory has been derived from measurements of the W dependence of the elastic differential cross sections d$\sigma$/d$t$ for both $\rho^0$ and $\phi$ mesons.

18 data tables

Differential cross section for proton-dissociative RHO0 photoproduction.

Differential cross section for elastic RHO0 photoproduction.

The ratio of the elastic to proton-dissociative cross sections for RHO0 photoproduction.

More…

Charmonium production in deep inelastic scattering at HERA

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Eur.Phys.J.C 10 (1999) 373-393, 1999.
Inspire Record 496430 DOI 10.17182/hepdata.44039

The electroproduction of J/psi and psi(2S) mesons is studied in elastic, quasi-elastic and inclusive reactions for four momentum transfers 2 < Q^2 < 80 GeV^2 and photon-proton centre of mass energies 25 < W < 180 GeV. The data were taken with the H1 detector at the electron proton collider HERA in the years 1995 to 1997. The total virtual photon-proton cross section for elastic J/psi production is measured as a function of Q^2 and W. The dependence of the production rates on the square of the momentum transfer from the proton (t) is extracted. Decay angular distributions are analysed and the ratio of the longitudinal and transverse cross sections is derived. The ratio of the cross sections for quasi-elastic psi(2S) and J/psi meson production is measured as a function of Q^2. The results are discussed in terms of theoretical models based upon perturbative QCD. Differential cross sections for inclusive and inelastic production of J/psi mesons are determined and predictions within two theoretical frameworks are compared with the data, the non-relativistic QCD factorization approach including colour octet and colour singlet contributions, and the model of Soft Colour Interactions.

17 data tables

Cross section for elastic J/PSI photoproduction in W bins.

Cross section for elastic J/PSI photoproduction in W bins.

Cross section for elastic J/PSI photoproduction in W bins.

More…

Elastic electroproduction of rho mesons at HERA.

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Eur.Phys.J.C 13 (2000) 371-396, 2000.
Inspire Record 495311 DOI 10.17182/hepdata.44043

The elastic electroproduction of rho mesons is studied at HERA with the H1 detector for a photon virtuality in the range 1 < Q^2 < 60 GeV^2 and for a hadronic centre of mass energy in the range 30 < W < 140 GeV. The shape of the pipi mass distribution in the rho resonance region is measured as a function of Q^2. The full set of rho spin density matrix elements is determined, and evidence is found for a helicity flip amplitude at the level of 8 +- 3 % of the non-flip amplitudes. Measurements are presented of the dependence of the cross section on Q^2, W and t (the four-momentum transfer squared to the proton). They suggest that, especially at large Q^2, the gamma^*p cross section develops a stronger W dependence than that expected from the behaviour of elastic and total hadron-hadron cross sections.

15 data tables

Average values of the spin density matrix elements measured for the 1996 data sample.

Spin density matrix elements measured for 3 Q**2 values for the 1996 data sample.

Spin density matrix elements measured for 3 W values for the 1996 data sample.

More…

Exclusive electroproduction of rho0 and J / psi mesons at HERA

The ZEUS collaboration Breitweg, J. ; Chekanov, S. ; Derrick, M. ; et al.
Eur.Phys.J.C 6 (1999) 603-627, 1999.
Inspire Record 475083 DOI 10.17182/hepdata.44217

Exclusive production of $\rho^0$ and $J/\psi$ mesons in e^+ p collisions has been studied with the ZEUS detector in the kinematic range $0.25 < Q^2 < 50 GeV^2, 20 < W < 167 GeV$ for the $\rho^0$ data and $2 < Q^2 < 40 GeV^2, 50 < W < 150 GeV$ for the $J/\psi$ data. Cross sections for exclusive $\rho^0$ and $J/\psi$ production have been measured as a function of $Q^2, W$ and $t$. The spin-density matrix elements $r^{04}_{00}, r^1_{1-1}$ and $Re r^{5}_{10}$ have been determined for exclusive $\rho^0$ production as well as $r^{04}_{00}$ and $r^{04}_{1-1}$ for exclusive $J/\psi$ production. The results are discussed in the context of theoretical models invoking soft and hard phenomena.

32 data tables

Exclusive RHO0 electro- and photo- production and cross sections as a function of Q**2 from the BPC data set.

Exclusive RHO0 electro- and photo- production cross section as a function of W from the BPC data set.

Exclusive RHO0 electro- and photo- production cross sections as a function of W from the DIS data set.

More…

Elastic and proton dissociative rho0 photoproduction at HERA

The ZEUS collaboration Breitweg, J. ; Derrick, M. ; Krakauer, D. ; et al.
Eur.Phys.J.C 2 (1998) 247-267, 1998.
Inspire Record 452353 DOI 10.17182/hepdata.44331

Elastic and proton-dissociative rho0 photoproduction (gamma p-->rho0 p,gamma p -->rho0 N,with rho0-->pi+pi-) has been studied in ep interactions at HERA for gamma-p centre-of-mass energies in the range 50<W<100 GeV and for |t|<0.5 GeV2; the results on the p-dissociative reaction are presented for masses of the dissociated proton system in the range MN^2<0.1W^2.For the elastic process,the pi+pi- invariant mass spectrum has been investigated as a function of t. As in fixed target experiments, the rho0 resonance shape is asymmetric;this asymmetry decreases with increasing |t|.The cross section has been studied as a function of W; a fit to the resonant part with the form W^a gives a=0.16\pm0.06(stat.) +0.11-0.15(syst.). The resonant part of the gamma p-->pi+pi- p cross section is 11.2\pm 0.1(stat.)+1.1-1.2 (syst.) mub at <W>=71.7 GeV. The t dependence of the cross section can be described by a function of the type Ae^(-b|t|+ct^2) with b=10.9\pm0.3(stat.)+1.0-0.5(syst.)GeV-2 and c=2.7\pm0.9(stat.)+1.9-1.7(syst.) GeV-4. The t dependence has also been studied as a function of W and a value of the slope of the pomeron trajectory 0.23\pm0.15(stat.)+0.10-0.07(syst.)GeV-2 has been deduced. The rho spin density matrix elements r^04_00,r^04_1-1 and Re[r^04_10] have been measured and found to be consistent with expectations based on SCHC. For p-dissociative pi+pi- photoproduction in the rho0 mass range, the distributions of the two-pion invariant mass, W and the polar and azimuthal angles of the pions in the helicity frame are the same within errors as those for the elastic process. The t distribution has been fitted to an exponential function with a slope parameter 5.8\pm0.3(stat.)\pm0.5(syst.)GeV-2. The ratio of the elastic to p-dissociative rho0 photoproduction cross section is 2.0\pm0.2(stat.)\pm0.7(syst.).

19 data tables

Integrated elastic rho0 photoproduction cross section.

Integrated elastic pi+ pi- photoproduction cross section.

Differential T distribution. Statistical errors only.

More…

Proton dissociative rho and elastic phi electroproduction at HERA

The H1 collaboration Adloff, C. ; Aid, S. ; Anderson, M. ; et al.
Z.Phys.C 75 (1997) 607-618, 1997.
Inspire Record 443293 DOI 10.17182/hepdata.44590

The electroproduction of rho mesons with proton diffractive dissociation for Q^2 > 7 GeV^2 and the elastic electroproduction of Phi mesons for Q^2 > 6 Gev^2 are studied in e^+ p collisions at HERA with the H1 detector, for an integrated luminosity of 2.8 pb-1. The dependence of the cross sections on P_t^2 and Q^2 is measured, and the vector meson polarisation obtained. The cross section ratio between proton dissociative and elastic production of rho mesons is measured and discussed in the framework of the factorisation hypothesis of diffractive vertices. The ratio of the elastic cross section for Phi and rho meson production is investigated as a function of Q^2.

11 data tables

Corrected PT**2 distribution for RHO production from the proton dissociative sample. Statistical errors only.

Cross sections and ratio of proton dissociative to elastic cross sections.

Cross sections and ratio of proton dissociative to elastic cross sections.

More…

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.

14 data tables

Statistical errors only.

Statistical errors only.

Cross section extrapolated to Q**2 = 0.

More…

Measurement of the Reaction $\gamma~* p \to \phi p$ in Deep Inelastic $e~+p$ Scattering at HERA

The ZEUS collaboration Derrick, M. ; Krakauer, D. ; Magill, S. ; et al.
Phys.Lett.B 380 (1996) 220-234, 1996.
Inspire Record 418041 DOI 10.17182/hepdata.44769

The production of $\phi$ mesons in the reaction $e~{+}p \rightarrow e~{+} \phi p$ ($\phi \rightarrow K~{+}K~{-}$), for $7 < Q~2 < 25$ GeV$~2$ and for virtual photon-proton centre of mass energies ($W$) in the range 42-134 GeV, has been studied with the ZEUS detector at HERA. When compared to lower energy data at similar $Q~2$, the results show that the $\gamma~*p \rightarrow \phid p$ cross section rises strongly with $W$. This behaviour is similar to that previously found for the $\gamma~*p \rightarrow \rho~0 p$ cross section. This strong dependence cannot be explained by production through soft pomeron exchange. It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small $x$. The ratio of $\sigma (\phi) / \sigma (\rho~0)$, which has previously been determined by ZEUS to be 0.065 $\pm$ 0.013 (stat.) in photoproduction at a mean $W$ of 70 GeV, is measured to be 0.18 $\pm $ 0.05 (stat.) $\pm$ 0.03 (syst.) at a mean $Q~2$ of 12.3 GeV$~2$ and mean $W$ of $\approx$ 100 GeV and is thus approaching at large $Q~2$ the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism.

4 data tables

No description provided.

Additional 32 PCT Systematic error.

Additional 32 PCT Systematic error.

More…

Elastic Photoproduction of $\rho~{0}$ Mesons at HERA

The H1 collaboration Aid, S. ; Andreev, V. ; Andrieu, B. ; et al.
Nucl.Phys.B 463 (1996) 3-32, 1996.
Inspire Record 415281 DOI 10.17182/hepdata.44784

The cross section for the elastic photoproduction of \r0\ mesons ($\gamma p \rightarrow \rho~0 p$) has been measured with the H1 detector at HERA for two average photon-proton centre-of-mass energies of 55 and 187GeV. TheFcenterline lower energy point was measured by observing directly the $\rho~{0}$ decay giving a cross section of $9.1\pm 0.9\,(\stat)\pm 2.5\,(\syst)\;\mu$b. The logarithmic slope parameter of the differential cross section, ${\rm d}\sigma/{\rm d}t$, is found to be $10.9 \pm 2.4\,(\stat) \pm 1.1\,(\syst)\;$GeV$~{-2}$. The \r0\ decay polar angular distribution is found to be consistent with s-channel helicity conservation. The higher energy cross section was determined from analysis of the lower part of the hadronic invariant mass spectrum of diffractive photoproduction and found to be $13.6\pm 0.8\,(\stat)\pm 2.4\,(\syst)\;\mu$b.

6 data tables

PI+ PI- cross section.

RHO0 cross section by selecting Mpipi to lie between 2Mpi and Mrho + 5width0.

No description provided.

More…

Vector Meson Production by Polarized Photons at 2.8-GeV, 4.7-GeV, and 9.3-GeV

Ballam, Joseph ; Chadwick, G.B. ; Eisenberg, Y. ; et al.
Phys.Rev.D 7 (1973) 3150, 1973.
Inspire Record 73602 DOI 10.17182/hepdata.43496

We present results on vector-meson photoproduction via γp→Vp in the LBL-SLAC 82-in. hydrogen bubble chamber exposed to a linearly polarized photon beam at 2.8, 4.7, and 9.3 GeV. We find ρ0 production to have the characteristics of a diffractive process, i.e., a cross section decreasing slowly with energy and a differential cross section with slope of ∼ 6.5 GeV−2. Within errors the ρ0 production amplitudes are entirely due to natural-parity exchange. s-channel helicity is conserved to a high degree in the γ→ρ0 transition. We find evidence for small helicity-flip amplitudes for ππ pairs in the ρ0 region. Photoproduction of ω mesons is separated into its natural- (σN) and unnatural- (σU) parity-exchange contributions. The Eγ and t dependence and the spin density matrix of the unnatural-parity-exchange contribution are consistent with a one-pion-exchange process. The natural-parity-exchange part has characteristics similar to ρ0 production. At 9.3 GeV the ratio of σ(ρ0) to σN(ω) is ∼ 7. The slope of the φ differential cross section is ∼ 4.5 GeV−2, smaller than that of ρ0 and ω production. Natural-parity exchange is the main contributor to φ production. No evidence for higher-mass vector mesons is found in ππ, πππ, or KK¯ final states. The s and t dependences of Compton scattering as calculated from ρ, ω, and φ photoproduction using vector-meson dominance agree with experiment, but the predicted Compton cross section is too small by a factor of 2.

47 data tables

No description provided.

No description provided.

No description provided.

More…

Exclusive $\rho^0$ and $\phi$ Production in Deep Inelastic Muon Scattering

The European Muon collaboration Ashman, J. ; Badelek, B. ; Baum, G. ; et al.
Z.Phys.C 39 (1988) 169, 1988.
Inspire Record 252743 DOI 10.17182/hepdata.15619

Data are presented on exclusive ρ0 and ϕ production in deep inelastic muon scattering from a target consisting mainly of nitrogen. The ratio of the total cross sections for ρ0 and ϕ production is found to be 9∶(1.6±0.4) at 〈Q2〉=7.5 GeV2, consistent with theSU(3) prediction of 9∶2. Thet dependence for exclusive ρ0 production is found to become shallover asQ2 increases and, for largeQ2, thet dependence is typical of that for a hard scattering process. Furthermore, the ratio of the cross sections for coherent: incoherent production from nitrogen is found to decrease rapidly withQ2. Such behaviour indicates that even for exclusive vector meson production the virtual photon behaves predominantly as an electromagnetic probe.

6 data tables

No description provided.

No description provided.

No description provided.

More…

EXCLUSIVE rho0 PRODUCTION IN DEEP INELASTIC MUON PROTON SCATTERING

The European Muon collaboration Aubert, J.J. ; Bassompierre, G. ; Becks, K.H. ; et al.
Phys.Lett.B 161 (1985) 203, 1985.
Inspire Record 214930 DOI 10.17182/hepdata.30353

Exclusive ϱ 0 production has been measured in 120, 200 and 280 GeV muon-proton interactions at high Q 2 (1 GeV 2 < Q 2 < 25 GeV 2 ) and W (6 GeV < W < 19 GeV). The photoproduction cross section decreases as 1/ Q 4 . A shallow t distribution, typical of a hard scattering process is observed and the ϱ 0 is found to be dominantly in the helicity zero spin state. The ϱ 0 s are mainly produced by transverse photons and s -channel helicity conservation seems to be invalid. The data cannot be described by the vector meson dominance model. These data show that at high Q 2 even exclusive ϱ 0 muoproduction is a hard scattering process and that the soft hadron-like properties of the photon have disappeared.

8 data tables

No description provided.

No description provided.

SYSTEMATIC ERROR ON SLOPE IN 0.8.

More…

Photoproduction of $\pi^+ \pi^- \pi^0$ on Hydrogen With Linearly Polarized Photons of Energy 20-{GeV} - 70-{GeV}

The Omega Photon & Bonn-CERN-Glasgow-Lancaster-Manchester-Paris-Rutherford-Sheffield collaborations Atkinson, M. ; Axon, T.J. ; Barberis, D. ; et al.
Nucl.Phys.B 231 (1984) 15-39, 1984.
Inspire Record 191169 DOI 10.17182/hepdata.33892

Results on photoproduction of π + π − π 0 in the photon energy range 20–70 GeV are presented. For the ω meson, the production cross-section is found to be 1010±15 (statistical)±290 (systematic) nb and is constant over the incident photon energy range. Spin-density matrix elements are evaluated for ω meson production. The φ meson is observed with a total photoproduction cross section (corrected for branching ratio to π + π − π 0 ) of 610±35±170 nb. A third resonance, at 1.67 GeV, is seen in the mass spectrum and its interpretation is discussed. The production of a broad π + π − π 0 continuum, mainly via ϱπ, and peaking at 1.2 GeV, contributes with a cross section of about 2.5 ωb. The spin-parity content is analysed by the moments of the π + π − π 0 decay angular distribution in the helicity frame and by maximum likelihood fits to the π + π − π 0 Dalitz plot. It is found that production of J P = 1 − states accounts for less than half of the total mass spectrum above 900 MeV. There is a broad enhancement in the 1 + wave around 1.15 GeV indicating photoproduction of the H(1190) meson.

6 data tables

No description provided.

EXPONENTIAL FITS TO D(SIG)/DT IN OMEGA MASS REGION.

EXPONENTIAL FITS TO D(SIG)/DT OVER FULL ENERGY FOR THREE MASS REGIONS CORRESPONDING TO OMEGA, PHI AND OMEGA*.

More…

ELECTROPRODUCTION OF PI DELTA AND OTHER NONDIFFRACTIVE FINAL STATES

Day, C.T. ; Harding, D.J. ; Klinger, J.S. ; et al.
Phys.Rev.D 23 (1981) 576-586, 1981.
Inspire Record 166699 DOI 10.17182/hepdata.24078

This paper reports the results of an experiment measuring the parameters of various electroproduction reactions for a range in the electroproduction variables 0.7<Q2<4 GeV2 and 2<W2<16 GeV2. This report is limited to nondiffractive exclusive channels, with detailed results regarding the πΔ final states, statistically limited results for KΛ final states, and upper limits on the production of a number of event topologies containing a single unseen neutral particle.

16 data tables

No description provided.

No description provided.

No description provided.

More…

Exclusive Vector Meson Production in Muon - Proton Scattering

del Papa, C. ; Dorfan, David E. ; Flatte, Stanley M. ; et al.
Phys.Rev.D 19 (1979) 1303, 1979.
Inspire Record 130570 DOI 10.17182/hepdata.24312

From a muon-proton scattering experiment with a streamer chamber at the Stanford Linear Accelerator we present results in the ranges 0.3<Q2<4.7 GeV2 and 1.7<W<4.7 GeV for the reactions μ+p→μpV where V is a vector meson (ρ0, ω, or φ). It is shown that in ρ production the skewing parameter and the longitudinal-transverse ratio change significantly as Q2 increases above 1 GeV2. The cross section for ρ0 production as a function of Q2 falls below the vector-meson-dominance prediction. The ratio of the cross section for exclusive vector-meson production to the total cross section falls by a factor of 10 between photoproduction and a Q2 of 2 GeV2, yet the ratio of ω to ρ production remains constant at the photoproduction value out to Q2>2 GeV2.

4 data tables

THE ABSOLUTE TOTAL CROSS SECTION IS FROM A FIT TO THE MIT-SLAC ELECTRON SCATTERING DATA BY W. ATWOOD AND S. STEIN.

No description provided.

FOR 0.6 < M(PI+ PI-) < 0.9 GEV, USING THE METHOD OF MOMENTS.

More…

Rho Production by Virtual Photons

Joos, P. ; Ladage, A. ; Meyer, H. ; et al.
Nucl.Phys.B 113 (1976) 53-92, 1976.
Inspire Record 108749 DOI 10.17182/hepdata.35708

The reaction γ V p → p π + π − was studied in the W , Q 2 region 1.3–2.8 GeV, 0.3–1.4 GeV 2 using the streamer chamber at DESY. A detailed analysis of rho production via γ V p→ ϱ 0 p is presented. Near threshold rho production has peripheral and non-peripheral contributions of comparable magnitude. At higher energies ( W > 2 GeV) the peripheral component is dominant. The Q 2 dependence of σ ( γ V p→ ϱ 0 p) follows that of the rho propagator as predicted by VDM. The slope of d σ /d t at 〈 Q 2 〉 = 0.4 and 0.8 GeV 2 is within errors equal to its value at Q 2 = 0. The overall shape of the ϱ 0 is t dependent as in photoproduction, but is independent of Q 2 . The decay angular distribution shows that longitudinal rhos dominate in the threshold region. At higher energies transverse rhos are dominant. Rho production by transverse photons proceeds almost exclusively by natural parity exchange, σ T N ⩾ (0.83 ± 0.06) σ T for 2.2 < W < 2.8 GeV. The s -channel helicity-flip amplitudes are small compared to non-flip amplitudes. The ratio R = σ L / σ T was determined assuming s -channel helicity conservation. We find R = ξ 2 Q 2 / M ϱ 2 with ξ 2 ≈ 0.4 for 〈 W 〉 = 2.45 GeV. Interference between rho production amplitudes from longitudinal and transverse photons is observed. With increasing energy the phase between the two amplitudes decreases. The observed features of rho electroproduction are consistent with a dominantly diffractive production mechanism for W > 2 GeV.

10 data tables

DIPION CHANNEL CROSS SECTION.

THE TOTAL CROSS SECTION WAS OBTAINED BY THE AUTHORS FROM A FIT TO THE SINGLE ARM DATA OF S. STEIN ET AL., PR D12, 1884 (1975).

No description provided.

More…

Study of rho0 Production in gamma d, gamma p and gamma n Reactions at 7.5-GeV/c Using Linearly Polarized Photon Beam

Alexander, G. ; Gandsman, J. ; Levy, A. ; et al.
Nucl.Phys.B 69 (1974) 445-453, 1974.
Inspire Record 94508 DOI 10.17182/hepdata.32344

The reaction γ d→d ππ , γ p→p ππ and γ n→n ππ were studied in the SLAC 82″ deuterium filled bubble chamber, exposed to a linearly polarized photon beam of 7.5 GeV. All three reactions are dominated by ϱ 0 production. The differential cross section has a slope of ∼6.5 GeV −2 for nucleon reactions and a slope of ∼27 GeV −2 for coherent deuteron reactions. The behaviour of the density matrix elements shows that ϱ production conserves s -channel c.m.s. helicity and is dominated by natural parity exchange.

1 data table

No description provided.


Vector meson production by 4.3 GeV polarized photons on deuterium

Eisenberg, Y. ; Haber, B. ; Kogan, E. ; et al.
Nucl.Phys.B 104 (1976) 61-97, 1976.
Inspire Record 98707 DOI 10.17182/hepdata.35922

Cross sections for γd and γn interactions and photoproduction of ϱ 0 and ω are studied at 4.3 GeV, using a linearly polarized photon beam in a deuterium bubble chamber. We find that σ T (γ n ) ⋍ σ T (γ p ) within about 5% and that the γn average charge multiplicity is lower than γp by 0.42±0.09. About 4000 ϱ 0 events and 70 coherent ω events are observed. We present total and differential cross sections for both xoherent and incoherent ϱ 0 production on deuterium, as well as decay angular distributions and density-matrix elements. We find that the t -channel isospin-one exchange amplitude in γ N → ϱ 0 N (e.g. A 2 exchange) is at most 5–13% of the dominant isoscalar amplituds. The ϱ 0 production mechanism is dominantly s -channel helicity-conserving (SHC) on both neutrons and protons. We find that relative to the SHC amplitudes, the single and double helicity-flip amplitudes at the γϱ 0 vertex are of the order of 10–15% for | t | > 0.25 GeV 2 , and have the same sign on both nucleons. This shows that helicity-flip is mainly due to isoscalar exchanges. The ratio of ω to ϱ 0 coherent forward cross sections is found to be 0.16±0.04. The natural-parity exchange part of γ N → ω N is strongly dominated by isoscalar exchanges, and the magnitude of the isovector-exchange is consistent with zero.

5 data tables

TOPOLOGICAL CROSS SECTIONS AND AVERAGE CHARGE MULTIPLICITIES GIVEN IN TABLE 1.

'PARAMETRIZATION'.

No description provided.

More…

Omega-Meson Production by Virtual Photons

Joos, P. ; Ladage, A. ; Meyer, H. ; et al.
Nucl.Phys.B 122 (1977) 365-382, 1977.
Inspire Record 118808 DOI 10.17182/hepdata.35453

Qausi-elastic ω production by ep scattering in the kinematic region 0.3. < Q 2 < 1.4 GeV 2 and 1.7 < W < 2.8 GeV was studied using a streamer chamber at DESY. The production angular distribution for γ V p → ω p has a strong non-peripheral component for W < 2 GeV. The ω production cross section falls by a factor of 4 as W changes from 1.7 to 2.8 GeV. In contrast the cross section for ω production with | t | < 0.5 GeV 2 is W independent between 1.7 and 2.8 GeV and for W > 2.0 GeV consistent in both W and Q 2 dependence with the predictions of a model based on one-pion exchange and diffraction.

5 data tables

FOR ALL T-VALUES. THE GAMMA* P TOTAL CROSS SECTION WAS TAKEN FROM A FIT TO THE DATA OF S. STEIN ET AL., PR D12, 1884 (1975). 'PPD'.

'PPD'. PERIPHERAL OMEGA PRODUCTION.

No description provided.

More…

A Comparative Study of rho0 Photoproduced on D, N and P at 7.5-GeV

Alexander, G. ; Benary, O. ; Gandsman, J. ; et al.
Nucl.Phys.B 104 (1976) 397-412, 1976.
Inspire Record 2982 DOI 10.17182/hepdata.35986

A 7.5 GeV linearly polarized photon beam was used to study ϱ 0 production on d, n and p in the SLAC 82 inch bubble chamber. The production of ϱ 0 is found to proceed mainly via t -channel natural parity exchange and to conserve s -channel c.m.s. helicity for small t . The I = 1 contribution to the γ N → ϱ 0 t -channel amplitude is found to be small at 7.5 GeV.

6 data tables

ERRORS QUOTED INCLUDE BOTH STATISTICAL AND SYSTEMATIC UNCERTAINTIES.

THE FOURTH REACTION IS THE SUM OF THE FIRST THREE, NAMELY THE CLOSURE DIFFERENTIAL CROSS SECTION.

DIPION EVENTS IN THE RHO0 MASS REGION (600 TO 880 MEV).

More…

Photoproduction of rho0 and rho- Mesons at 3-GeV

Bapu, P. ; Endorf, R. ; Meadows, B. ; et al.
Phys.Rev.D 15 (1977) 26, 1977.
Inspire Record 123802 DOI 10.17182/hepdata.24621

The photoproduction of ρ0 and ρ− mesons has been studied at 3 GeV in the reactions γd→dπ±π−, γd→psnπ+π−, and γd→pspπ−π0. For ρ0 and ρ− production in these reactions we present the total and differential cross sections, the decay angular distributions, and the spin density matrix elements. The photoproduction of the ρ0 is found to be consistent with s-channel helicity conservation and is dominated by natural-parity exchange. The ρ− meson production has approximately equal natural- and unnatural-parity-exchange contributions. The unnatural-parity-exchange contribution is consistent with one-pion exchange and is used to estimate the value of Γρπγ.

6 data tables

No description provided.

No description provided.

No description provided.

More…

Coherent Photoproduction of Vector Mesons on Deuterium at 5.5-GeV

Gupta, Virendra Prakash ; Fung, S.Y. ; Oh, Y.T. ; et al.
Phys.Rev.D 14 (1976) 42-54, 1976.
Inspire Record 115714 DOI 10.17182/hepdata.24672

Coherent photoproduction of vector mesons ρ0, ω, φ, and ρ′ on deuterium was studied using the SLAC 82-in. bubble chamber exposed to linearly polarized photons at 5.5 GeV. The reaction channel γd→π+π−d was studied in detail. Nine independent density-matrix parameters have been determined from the ρ0 decay distribution. ρ production in this channel was found to proceed almost completely through natural-parity exchange for |t|≤0.25 GeV2 and conserve s-channel c.m. helicity for |t|≤0.15 GeV2. A measurement of differential cross section for this channel has been made.

3 data tables

POLARIZED PHOTON - VECTOR MESON DENSITY MATRICES ARE EXPLAINED BY SCHILLING/SEYBOTH/WOLF NP B15, 397 (1970). 'SH' - HELICITY FRAME..............Z = 3,RF = 1-2. 'TH' - GOTTFRIED-JACKSON FRAME.....Z = 1,RF = 3. 'ADAIR' - ADAIR FRAME..............Z = 1,RF = 1-2.

No description provided.

ERROR INCLUDES BACKGROUND UNCERTAINTY.