Measurements of the antiproton-proton annihilation cross-section in the beam momentum range between 180 and 600 MeV/c

We show that all central rapidity hadron yields measured in Pb-Pb collisions at √ s NN = 2.76 TeV are well described by the chemical nonequilibrium statistical hadronization model (SHM), where the chemically equilibrated quark-gluon plasma source breaks up directly into hadrons. SHM parameters are obtained as a function of centrality of colliding ions, and we compare CERN Large Hadron Collider (LHC) results with Brookhaven National Laboratory Relativistic Heavy Ion Collider (RHIC) results. We predict yields of unobserved hadrons and address antimatter production. The physical properties of the quark-gluon plasma fireball particle source show universality of hadronization conditions at LHC and RHIC.

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“…In a wide range of low relative energies, which are relevant here, the event cross section is [48] σ event ≡ σ annih v/c 46 mb.…”

Section: B P/π Ratio and Chemical (Non-)equilibriummentioning

confidence: 99%

Hadron production and quark-gluon plasma hadronization in Pb-Pb collisions atsNN=2.76 TeV

et al. 2013

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“…Low energy N?4 scattering is reanalyzed using the new data on annihilation cross-sections from CERN [1], the tip-absorption measurement from BNL [-2] and the annihilation width of the 2p state in antiprotonic hydrogen [-3]. Imposing the condition that the imaginary part of the effective range is negative we find low energy scattering parameters which interpolate between the existing ITEP [4] and CERN/Heidelberg [5] values.…”

mentioning

confidence: 97%

“…The low-energy annihilation cross-section [1] incorporating the region below 300 MeV/c where the data points were previously absent;…”

mentioning

confidence: 99%

Updating the effective range expansion of low-energyN $$\bar N$$ -scattering

Pirner

Kerbikov

Mahalanabis

1991

Z. Physik A - Hadrons and Nuclei

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Low energy N?4 scattering is reanalyzed using the new data on annihilation cross-sections from CERN [1], the tip-absorption measurement from BNL [-2] and the annihilation width of the 2p state in antiprotonic hydrogen [-3]. Imposing the condition that the imaginary part of the effective range is negative we find low energy scattering parameters which interpolate between the existing ITEP [4] and CERN/Heidelberg [5] values. PACS: 13.75.-n; 13.75.cs Experiments in low energy NbT-scattering have developed greatly since the operation of the LEAR facility at CERN has started. Besides the NN and the ~N interactions antinucleon-nucleon scattering is the third test of our limited understanding of hadronic interactions. A comparison of N/V-intermediate range potentials with NN-potentials is perhaps the only chance to find the range where the meson-exchange picture breaks down and subnucleonic constituent interchange takes over. Unfortunately the strong NN-annihilation masks such a simple picture and only careful comparison to the data will clarify the situation.In this paper we follow up a model independent analysis of the low energy NiV interaction with the effective range expansion [4,5]. Previously there have been two quite different solutions obtained from the data with pc<300 MeV/c. The CERN/Heidelberg fit [5] used more experimental data than the ITEP fit [4]. But this alone cannot explain the discrepancy. In the ITEP fit the effective range is restricted to be real, whereas in the CERN/Heidelberg fit it is unconstrained besides the condition that each partial wave amplitude is unitary in the considered momentum range. The argument for * Supported by the BMFT-grant 06 HD 756 ** Institute for Theoretical and Experimental Physics (ITEP), Moscow, USSR *** Saha Institute of Nuclear Physics, Calcutta, India a real effective range in the ITEP fit was that there are no important annihilation thresholds close to the NN threshold. Then the phase space in the annihilation thresholds close to the NN threshold. Then the phase space in the annihilation channel changes only by about 10% within the interval of the incident i0 momentum 0 0, a negative imaginary r gives a consistently negative imaginary part in the denominator and 4~z consequently a positive cross section a1 = o = ~-Im F~ = o.In addition to the theoretica...

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“…from (23). To this end we have used the best available data on pp~r+~ - [19] and combined them with the annihilation cross section of [20]. In the momentum interval where these two measurements overlap the ratio a (~r +Tr-)/aa has been deduced.…”

Section: )mentioning

confidence: 99%

“…For example, the two versions of the Dover-Richard model lead for the 13S~ level to I/=0.075 and ~/=0.16, respectively [12]. Thus we can either end up with (20) and (22) or invoke some approximations which are not based on a sound theoretical basis and to a great extent suffer from the flaw already mentioned in relation to (4): the ambiguity of the extrapolation of the in flight data towards threshold. Nevertheless, we shall try to estimate ~/ from available data for the reason that these estimates will provide evidence that r/is channel dependent.…”

Section: )mentioning

confidence: 99%

The $$\bar pp \to e^ + e^ - $$ reaction at rest and the hierarchy of the annihilation ranges

Kerbikov

Kondratyuk

1991

Z. Physik A - Hadrons and Nuclei

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A new procedure is devised to evaluate the proton formfactor at the pp threshold from experimental data on pp--*e+e -annihilation at rest. Comparison of the pp~e + e-and pp~zc + re-processes reveals that annihilation ranges for various channels are ranked in line with quark dynamics. PACS: 12.35.Ht; 13.75.Cs Antiproton-proton annihilation at low energy into e + epair has been studied intensively in recent years at the Low-Energy Antiproton Ring (LEAR) at CERN. The experiment PSl70 (APPLE) has completed data taking [ 1 ] and the first results of the analysis have been presented [2]. Our purpose in this note is to elucidate some properties of the low-energy pp--*e + e-annihilation which to our knowledge have been glossed over in the literature. In connection with the pp---, e +e-reaction we also want to make some remarks on the problem of the annihilation range which has devoted a lot of debates in the literature in recent years.We start by raising the following seemingly trivial question: given the experimental value of the ratio R = fLH ( e+ e-)/fLH (Z~ + re --) of the frequencies ofpp annihilation at rest in liquid hydrogen into e + e-and rc + rcpairs how to extract the threshold value of the proton electromagnetic formfactor. The standard procedure [3] goes roughly as follows: the ratio R measured with p brought to rest is set equal to the ratio of the corresponding partial widths of the antiprotonic hydrogen To allow the determination of G the zero energy limit of vo (~ + ~r -) is needed. This quantity was obtained either by direct extrapolation of a (n + re -) from the momentum region PL > 160 MeV/c [6], or by extrapolation of the total pp cross section towards threshold and then multiplying the extrapolated value by the branching ratio B~ + ~_ at rest. The determination of the formfactor along these lines performed already long ago yielded the result[3]G=0.51_+0.08. (5)Since that time some progress has been made in our understanding of N29 physics, new experimental information has been collected (see, e.g. the review paper [7]), and given this development the above evaluation of the formfactor is suspected of not delivering the most reliable results. In our view the shortcomings of the above procedure are the following: (i) the ambiguity of the extrapolation procedure, (ii) the implicit assumption that the quantity I ~' (0) ]z is the same in (2) and (3), and (iii) the neglect of the pp~zr + zc -annihilation from P-waves in liquid hydrogen. The concern over the first of these points

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Measurements of the antiproton-proton annihilation cross-section in the beam momentum range between 180 and 600 MeV/c

Cited by 21 publications

References 25 publications

Hadron production and quark-gluon plasma hadronization in Pb-Pb collisions atsNN=2.76 TeV

Hadron production and quark-gluon plasma hadronization in Pb-Pb collisions atsNN=2.76 TeV

Updating the effective range expansion of low-energyN $$\bar N$$ -scattering

The $$\bar pp \to e^ + e^ - $$ reaction at rest and the hierarchy of the annihilation ranges

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