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The proton and deuteron F_2 structure function at low Q^2

Tvaskis, V. ; Arrington, J. ; Asaturyan, R. ; et al.

Phys.Rev.C 81 (2010) 055207, 2010.

Inspire Record 844968 DOI 10.17182/hepdata.56742

Measurements of the proton and deuteron $F_2$ structure functions are presented. The data, taken at Jefferson Lab Hall C, span the four-momentum transfer range $0.06 < Q^2 < 2.8$ GeV$^2$, and Bjorken $x$ values from 0.009 to 0.45, thus extending the knowledge of $F_2$ to low values of $Q^2$ at low $x$. Next-to-next-to-leading order calculations using recent parton distribution functions start to deviate from the data for $Q^2<2$ GeV$^2$ at the low and high $x$-values. Down to the lowest value of $Q^2$, the structure function is in good agreement with a parameterization of $F_2$ based on data that have been taken at much higher values of $Q^2$ or much lower values of $x$, and which is constrained by data at the photon point. The ratio of the deuteron and proton structure functions at low $x$ remains well described by a logarithmic dependence on $Q^2$ at low $Q^2$.

62 data tables

Table 1

Proton and Deuteron F2 structure function for an x value of 0.040, determined via the Rosenbluth separation method. Error is shown without the contribution from radiative corrections.

Table 2

Proton and Deuteron F2 structure function for an x value of 0.060, determined via the Rosenbluth separation method. Error is shown without the contribution from radiative corrections.

Table 3

Proton and Deuteron F2 structure function for an x value of 0.080, determined via the Rosenbluth separation method. Error is shown without the contribution from radiative corrections.

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Delta Delta Excitation in Proton-Proton Induced pi0pi0 Production

Skorodko, T. ; Bashkanov, M. ; Bogoslawsky, D. ; et al.

Phys.Lett.B 695 (2011) 115-123, 2011.

Inspire Record 860341 DOI 10.17182/hepdata.56497

Exclusive measurements of the $pp \to pp\pi^0\pi^0$ reaction have been performed at CELSIUS/WASA at energies from threshold up to $T_p$ = 1.3 GeV. Total and differential cross sections have been obtained. Here we concentrate on energies $T_p \ge$ 1 GeV, where the $\Delta\Delta$ excitation becomes the leading process. No evidence is found for a significant ABC effect beyond that given by the conventional $t$-channel $\Delta\Delta$ excitation. This holds also for the double-pionic fusion to the quasibound $^2$He. The data are compared to model predictions, which are based on both pion and $\rho$ exchange. Total and differential cross sections are at variance with these predictions and call for a profound modification of the $\rho$-exchange. A phenomenological modification allowing only a small $\rho$ exchange contribution leads to a quantitative description of the data.

33 data tables

Table 1

Cross section taken from an earlier CELSIUS publication (PL B679(2009)30 - arXiv:0903.2087).

Table 2

PI0_PI0 invariant mass distribution at an incident kinetic energy of 1000 MeV.

Table 3

PI0_PI0 invariant mass distribution at an incident kinetic energy of 1100 MeV.

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Measurement of $\pi^0 \Lambda$, $\bar{K}^0 n$, and $\pi^0 \Sigma^0$ production in $K^- p$ interactions for $p_{K^-}$ between 514 and 750 MeV/$c$

Prakhov, S. ; Nefkens, B.M.K. ; Bekrenev, V. ; et al.

Phys.Rev.C 80 (2009) 025204, 2009.

Inspire Record 804864 DOI 10.17182/hepdata.52376

The results on the differential cross sections as well as the polarizations of $\Lambda$ and $\Sigma^0$ have been obtained for $\bar{K}^0 n$, $\pi^0 \Lambda$, and $\pi^0 \Sigma^0$ production in $K^- p$ interactions at eight $K^-$ momenta between 514 and 750 MeV/$c$. The study is conducted by measuring multiphoton final states with the Crystal Ball spectrometer, using a $K^-$ beam from the Alternating Gradient Synchrotron of BNL. The results improve substantially the existing data, allowing a detailed reexamination of the $\Lambda^*$ and $\Sigma^*$ states in our energy range.

11 data tables

Table 1

Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.

Table 2

Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.

Table 3

Differential cross section for the K- P --> PI0 LAMBDA reaction. Errors are statistical only.

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Neutron-proton charge-exchange amplitudes at 585-MeV

Chiladze, D. ; Carbonell, J. ; Dzyuba, A. ; et al.

2008.

Inspire Record 803150 DOI 10.17182/hepdata.52344

The differential cross section and deuteron analysing powers of the dp -> {pp}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170 MeV, data were obtained for small momentum transfers to a {pp} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable.

6 data tables

Table 1

Differential cross section for the unpolarized DEUT P --> P P N reaction integrated over momentum transfer Q < 100 MeV.

Table 2

Unpolarized differential cross section for the DEUT P --> P P N reaction of (P P) excitation energies < 3 MeV.

Table 3

Spherical tensor analysing powers t20 and t22 for EPP 0.1 to 1.0 MeV and cos(theta) > 0.5.

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Exclusive measurement of two-pion production in the dd --> 4Hepipi reaction

Keleta, S. ; Bargholtz, Chr. ; Bashkanov, M. ; et al.

Nucl.Phys.A 825 (2009) 71-90, 2009.

Inspire Record 818215 DOI 10.17182/hepdata.52982

The results from the first kinematically complete measurement of the dd --> 4Hepipi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pipi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV, with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pipi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN--> dpi sub-processes.

15 data tables

Table 1

Total cross section for neutral and charged pion channels.

Table 2

Invariant PI0 PI0 mass distribution at deuteron kinetic energy 1.029 GeV.

Table 3

Invariant PI+ PI- mass distribution at deuteron kinetic energy 1.029 GeV.

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Measurement of 3pi^0 photoproduction on the proton from threshold to 1.4 GeV

Starostin, A. ; Suarez, I.M. ; Nefkens, B.M.K. ; et al.

2011.

Inspire Record 884723 DOI 10.17182/hepdata.57591

The total cross section for gamma p -> 3pi0 p has been measured for the first time from threshold to 1.4 GeV using the tagged photon beam of the Mainz Microtron. The equipment utilized the Crystal Ball multiphoton spectrometer, the TAPS forward detector and a particle identification detector. The gamma p -> 3pi0 p total cross section has two broad enhancements at sqrt{s}~1.5 GeV and 1.7 GeV. We obtained the ratio of the total cross sections gamma p -> 3pi0 p to gamma p -> eta p equal to 0.014 \pm 0.001 at sqrt{s}~1.5 GeV.

1 data table

Table 1

The measured total cross section with statistical errors.