High precision measurement of the associated strangeness production in proton proton interactions

The COSY-TOF collaboration Jowzaee, S. ; Borodina, E. ; Clement, H. ; et al.
Eur.Phys.J. A52 (2016) 7, 2016.
Inspire Record 1393330 DOI 10.17182/hepdata.70735

A new high precision measurement of the reaction pp -> pK+Lambda at a beam momentum of 2.95 GeV/c with more than 200,000 analyzed events allows a detailed analysis of differential observables and their inter-dependencies. Correlations of the angular distributions with momenta are examined. The invariant mass distributions are compared for different regions in the Dalitz plots. The cusp structure at the N Sigma threshold is described with the Flatt\'e formalism and its variation in the Dalitz plot is analyzed.

9 data tables

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Single pi- production in np collisions for excess energies up to 90-MeV

The COSY-TOF collaboration Abdel-Bary, M. ; Brinkmann, K.-Th. ; Clement, H. ; et al.
Eur.Phys.J. A36 (2008) 7-16, 2008.
Inspire Record 759337 DOI 10.17182/hepdata.66229

The quasifree reaction $np\to pp\pim$ was studied in a kinematically complete experiment by bombarding a liquid hydrogen target with a deuteron beam of momentum 1.85 GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector $\mathbb{P}_n$ which differed from event to event. A range of almost 90 MeV excess energy above threshold was covered. Energy dependent angular distributions, invariant mass spectra as well as fully covered Dalitz plots were deduced. Sizeable $pp$ FSI effects were found as were contributions of $p$ and $d$ partial waves. The behavior of the elementary cross section $\sigma_{01}$ close to threshold is discussed in view of new cross section data. In comparison with existing literature data the results provide a sensitive test of the spectator model.

4 data tables

Differential cross sections in $\mu b/sr$ for the angular distributions of the relative proton momentum at six excess energies Q.

Expansion coefficients of the Legendre polynomial fits to the angular distributions of the relative proton momentum.

Differential cross sections in $\mu b/sr$ for the angular distributions of the pion angular momentum at six excess energies Q.

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On the Production of pi+ pi+ Pairs in pp Collisions at 0.8- GeV

The COSY-TOF collaboration Abd El-Samad, S. ; Bilger, R. ; Brinkmann, K.-Th. ; et al.
Eur.Phys.J. A42 (2009) 159-161, 2009.
Inspire Record 823367 DOI 10.17182/hepdata.52421

Data accumulated recently for the exclusive measurement of the $pp\to pp\pi^+\pi^-$ reaction at a beam energy of 0.793 GeV using the COSY-TOF spectrometer have been analyzed with respect to possible events from the $pp \to nn\pi^+\pi^+$ reaction channel. The latter is expected to be the only $\pi\pi$ production channel, which contains no major contributions from resonance excitation close to threshold and hence should be a good testing ground for chiral dynamics in the $\pi\pi$ production process. No single event has been found, which meets all conditions for being a candidate for the $pp \to nn \pi^+\pi^+$ reaction. This gives an upper limit for the cross section of 0.16 $\mu$b (90% C.L.), which is more than an order of magnitude smaller than the cross sections of the other two-pion production channels at the same incident energy.

1 data table

Upper limit to the P P --> N N PI+ PI+ cross section.


Single-Pion Production in pp Collisions at 0.95-GeV/c. II.

The COSY-TOF collaboration Abd El-Samad, S. ; Bilger, R. ; Brinkmann, K.-Th. ; et al.
Eur.Phys.J. A39 (2009) 281-289, 2009.
Inspire Record 790164 DOI 10.17182/hepdata.50496

The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and $pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. Main emphasis is put on the presentation and discussion of the $np\pi^+$ channel, since the results on the other channels have already been published previously. The total and differential cross sections obtained are compared to theoretical calculations. In contrast to the $pp\pi^0$ channel we find in the $np\pi^+$ channel a strong influence of the $\Delta$ excitation already at this energy close to threshold. In particular we find a $(3 cos^2\Theta + 1)$ dependence in the pion angular distribution, typical for a pure s-channel $\Delta$ excitation and identical to that observed in the $d\pi^+$ channel. Since the latter is understood by a s-channel resonance in the $^1D_2$ $pn$ partial wave, we discuss an analogous scenario for the $pn\pi^+$ channel.

6 data tables

Differential cross section for the process P P --> P N PI+ as a function ofthe P PI+ mass.

Differential cross section for the process P P --> P N PI+ as a function ofthe N PI+ mass.

Differential cross section for the process P P --> P N PI+ as a function ofthe P N mass.

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Comparison of isoscalar vector meson production cross-sections in proton-proton collisions

The COSY-TOF collaboration Abdel-Bary, M. ; Abdel-Samad, S. ; Brinkmann, K.-Th. ; et al.
Phys.Lett. B647 (2007) 351-357, 2007.
Inspire Record 745517 DOI 10.17182/hepdata.31471

The reaction $ pp\to pp\bf \omega$ was investigated with the TOF spectrometer, which is an external experiment at the accelerator COSY (Forschungszentrum Julich, Germany). Total as well as differential cross sections were determined at an excess energy of $93 MeV$ ($p_{beam}=2950 MeV/c$). Using the total cross section of $(9.0\pm 0.7 \pm1.1) \mu b$ for the reaction $ pp\to pp\omega$ determined here and existing data for the reaction $pp\to pp\bf \phi$, the ratio $\mathcal{R}_{\phi/\omega}=\sigma_\phi/\sigma_\omega$ turns out to be significantly larger than expected by the Okubo-Zweig-Iizuka (OZI) rule. The uncertainty of this ratio is considerably smaller than in previous determinations. The differential distributions show that the $\omega$ production is still dominated by S-wave production at this excess energy, however higher partial waves clearly contribute. A comparison of the measured angular distributions for $\omega$ production to published distributions for $\phi$ production at $83 MeV$ shows that the data are consistent with an identical production mechanism for both vector mesons.

5 data tables

Total cross section after acceptance correction and normalization.

Differential cross section as a function of the cosine of the polar angle of the protons in the overall c.m. system.

Differential cross section as a function of the omega meson angle in the overall c.m. system.

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Single-Pion Production in pp Collisions at 0.95-GeV/c (I)

The COSY-TOF collaboration El-Samad, S Abd ; Bilger, R. ; Brinkmann, K.-Th. ; et al.
Eur.Phys.J. A30 (2006) 443-453, 2006.
Inspire Record 725793 DOI 10.17182/hepdata.43429

The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and $pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus all pion production channels were recorded with 1-4 overconstraints. The total and differential cross sections obtained are compared to previous data and theoretical calculations. Main emphasis is put on the discussion of the $pp\pi^0$ channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement with recent phenomenological and theoretical predictions. In particular we observe very large anisotropies for the $\pi^0$ angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip transitions associated with $\pi^0$ $s$- and $d$-partial waves and emphasizing the important role of $\pi^0$ d-waves.

8 data tables

Total cross section measurements.. Errors are mainly systematic.

Measured angular distribution for elastic P P scattering in the CM system normalised to the data in the SAID database (Arndt et al. PR C62,034005(2000). This measurement is made to determine the luminosity.

The measured pion angular distribution in the CM system in the reaction P P --> DEUT PI+.

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Hyperon production in the channel p p ---> K+ Lambda p near the reaction threshold

The COSY-TOF collaboration Abdel-Samad, S. ; Bilger, R. ; Bohm, A. ; et al.
Phys.Lett. B632 (2006) 27-34, 2006.
Inspire Record 710561 DOI 10.17182/hepdata.26998
7 data tables

Measured total cross sections.

Distribution of the invariant mass of the P-LAMBDA subsystem at beam momentum 2.85 GeV.

Distribution of the invariant mass of the K-LAMBDA subsystem at beam momentum 2.85 GeV.

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Study of the reaction p p ---> p p pi0 within 10-MeV above the threshold

The COSY-TOF collaboration AbdEl Samad, S. ; Bilger, R. ; Bohm, A. ; et al.
Eur.Phys.J. A17 (2003) 595-606, 2003.
Inspire Record 605377 DOI 10.17182/hepdata.43625

Kinematically complete measurements of the $pp\to pp\pi^{0}$ reaction were performed for beam energies in the range $292 - 298 $MeV. By detecting both protons in coincidence with the large acceptance COSY-TOF spectrometer set up at an external beam line of the proton synchrotron COSY-Julich, total and differential cross sections and energy distributions were obtained. A strong enhancement is observed in the Dalitz plots resulting from the final state interaction between the outgoing proton pair: the data are well reproduced by Monte Carlo simulations with standard parameters for scattering length $a_0$=-7.83 fm and effective range $r_0$=2.8 fm. The total cross sections exceed the ones measured recently in internal target experiments at IUCF and CELSIUS by roughly 50%. Arguments are presented which link this discrepancy with the effect of the final state interaction pushing yield into the very small-angle region and the near-impossibility of an internal target experiment to cover just this range.

1 data table

Total P P --> P P PI0 cross section.


Measurement of the eta production in proton proton collisions with the COSY time-of-flight spectrometer

The COSY-TOF collaboration Abdel-Bary, M. ; Abdel-Samad, S. ; Bilger, R. ; et al.
Eur.Phys.J. A16 (2003) 127-137, 2003.
Inspire Record 587236 DOI 10.17182/hepdata.43626

The reaction pp -> pp eta was measured at excess energies of 15 and 41 MeV at an external target of the Juelich Cooler Synchrotron COSY with the Time of Flight Spectrometer. About 25000 events were measured for the excess energy of 15 MeV and about 8000 for 41 MeV. Both protons of the process pp eta were detected with an acceptance of nearly 100% and the eta was reconstructed by the missing mass technique. For both excess energies the angular distributions are found to be nearly isotropic. In the invariant mass distributions strong deviations from the pure phase space distributions are seen.

6 data tables

Angular distribution of the ETA in the CM frame.

Angular distribution of the P P momentum in the CM frame.

Squared P P invariant mass distribution.

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Production of omega mesons in proton proton collisions

The COSY-TOF collaboration Abd El-Samad, S. ; Abdel-Bary, M. ; Brinkmann, K.T. ; et al.
Phys.Lett. B522 (2001) 16-21, 2001.
Inspire Record 559945 DOI 10.17182/hepdata.47093

The cross section for the production of $\omega$ mesons in proton-proton collisions has been measured in a previously unexplored region of incident energies. Cross sections were extracted at 92 MeV and 173 MeV excess energy, respectively. The angular distribution of the $\omega$ at $\epsilon$=173 MeV is strongly anisotropic, demonstrating the importance of partial waves beyond pure s-wave production at this energy.

2 data tables

Measured cross sections for omega production.

Angular distribution of the OMEGA in the overall centre-of-momentum frame. Statistical error only.