The intensity interferometry technique, commonly referred to as the Hanbury-Brown/Twiss effect, has been applied to nuclear and elementary-particle collisions as a method of investigating their space-time evolution. In this review the theoretical framework of the technique is presented, describing the formulations in common use. A survey is made of its application to subatomic collisions, ranging from high-energy elementary-particle reactions to low-energy nuclear reactions. Results derived from experimental data analysis are compiled and discussed. A critique is made of the interpretational difficulties associated with the use of the technique in reaction studies.

Intensity interferometry in subatomic physics

Do we see the phase transition hadron → quark-gluon plasma (predicted by so many models) at pp collider energies? Yes; we even see it alrealy at ISR energies. This conclusion might only be escaped if all speculations and calculations about this phase transition and the use of statistical thermodynamics in this context are senseless and if the consistency (though not detailed agreement) of their predictions with the experiment is due to some most unlikely accident. The various distorting mechanisms entering between idealized thermodynamics and real collisions may affect numerical values; they cannot invalidate our conclusion.

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Multiplicities,p T distributions and the expected hadron → quark-gluon phase transition

The physics of nucleon-antinucleon annihilation

https://www1.cb.uni-bonn.de/fileadmin/user_upload/internal/Publication/Publication_PhysRept_413_2005_KlemptEtAl.pdf

The antinucleon-nucleon interaction at low energy: annihilation dynamics

We study ¯pp annihilation at rest intoπφ andγφ. Rescattering by ¯K*K+K*¯K and ρ+ρ− for ¯pp→πφ states is sizable, of order (0.90 to 2.6) × 10−4 in the branching ratio, but smaller than experiment. For ¯pp→γφ the rescattering contributions are negligible, but theγφ channel is well explained by aρφ intermediate state combined with vector meson dominance.

Rates for the reactions $$\bar pp \to \pi \phi $$ and? ?

We have analysed the three-body annihilations at rest $\overline p n \to K\overline K \pi $, from a total sample of 2.22·105 annihilations. The annihilation at rest $\overline p n \to K\overline K \pi $ has been studied by Conforto et al. The « multiple final-state interaction model » developed by them has been used to analyse the Open image in new window annihilation; an overall consistent picture is obtained in this way.

The annihilation at rest → K\overline K \pi π

We have analysed 2.22·105$\bar pn$ annihilations at rest into final states with two K-mesons and pions. The annihilation rates into three-body ($K\bar K\pi $) and four-body ($K\bar K\pi \pi $) final states are found to be comparable, whereas the rates for the five-body states ($K\bar K\pi \pi \pi $) are one order of magnitude lower, with the exception of the rate for the quasi-three-body state K−K10ω. No signal for the production of the Kππ resonance C or for the$K\bar K\pi $ resonance E is observed. These results are compatible with the production of C and E mesons from$\bar pp$ annihilations at rest if the 0216 isospin of C is 1/2 and that of E is 0, but not ifI(C)=3/2 andI(E)=1.

Annihilations$\bar pn$ n at rest into final states containing K-mesons

From an exposure of the CERN 2 m HBC to a separated$\bar p$ beam at 12 GeV/c we got ∼90 000 pictures. The topological cross-sections are reported. A fairly systematic investigation of 1098 events fitting the reaction$\bar pp \to \bar pp\pi ^ - \pi ^ + $ is presented. We looked also for the channels$\bar pp \to \pi ^ - \pi ^ - \pi ^ + \pi ^ + $ and$\bar pp \to \bar p\bar ppp$. The cross-section for$\bar pp \to \bar pp\pi ^ - \pi ^ + $ is (2.35 ± 0.25) mb. Various experimental distributions are well described by two versions of the one-pion exchange model. In the first one off-shell corrections are applied by introducing form factors (OPEM), whereas in the other model the exchanged pion is Reggeized (RPEM). Large production of Δ++(1236) and$\overline {\Delta + + } (1236)$ is observed. dσ/dt and$\sigma (\bar \Delta \Delta )$ for the reaction$\bar pp \to \overline {\Delta + + } \Delta ^{ + + } $ have been determined by a maximum-likelihood fit which takes into account the peripheral nature of the interaction:$\sigma (\bar \Delta \Delta ) = (0.64 \pm 0.07)$. There is evidence for ρ0 production ((40 ÷ 120) µb) and a suggestion of a peak at 1.72 GeV in the combined mass distribution of the systems pπ+π− and$\bar p\pi ^ + \pi ^ - $. For the 302 events in the double-isobar region 12 independent statistical tensors connected with the joint decay angular distribution have been determined. They have been compared with the prediction of a simple OPE model with absorptive corrections. The relations among statistical tensors, which follow from the assumption of additivity in quark models, have been tested in the Jackson frame. Within the large experimental errors they are found to be satisfied. Since the inclusion of the peripheral effect, neglected in previous experiments, affects the determination of the$\bar \Delta \Delta $ cross-section,$\sigma (\bar \Delta \Delta )$ has been re-evaluated for two experiments at 3.6 and 5.7 GeV/c and is (2.4 ± 0.2) mb and (1.45 ± 0.2) mb, respectively. The dependence of$\sigma (\bar \Delta \Delta )$ on the primary momentum agrees with the prediction of the OPE model.

The reaction$\bar pp \to \bar pp\pi ^ - \pi ^ + $ at 12 GeV/cat 12 GeV/c

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Erratum to: Observation of interference correlations between like pions in the reaction $$\bar pp \to 2\pi ^ + 2\pi ^ - \pi ^0 $$ at low energyat low energy

The reactions
 

$$\bar pp$$


 → 3π−3π+ and
 

$$\bar pp$$


 → 3π−3π+π0 have been studied at 1.00, 1.04 and 1.13 GeV/c incident momentum. Total cross-sections and angular distributions are presented. The contributions of the various intermediate states to the final states have been determined by the maximum-likelihood method. The most important intermediate states result to be eeρ in the 6π annihilation and eρω in the 7π annihilation.

C. Petri

Papers

The annihilation at rest → K\overline K \pi π

Annihilations\(\bar pn\) n at rest into final states containing K-mesons

The reaction\(\bar pp \to \bar pp\pi ^ - \pi ^ + \) at 12 GeV/cat 12 GeV/c

Erratum to: Observation of interference correlations between like pions in the reaction $$\bar pp \to 2\pi ^ + 2\pi ^ - \pi ^0 $$ at low energyat low energy

Experimental study of 6-prong events in \bar pp annihilation around 1 GeV/c