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Multi-Body Phenomena in Strong Interactions

  • M. Jacob
Part of the NATO Advanced Study Institutes Series book series (volume 4)

Abstract

A survey of research at the CERN Intersecting Storage Rings during the last year, this paper deals with five main topics: Elastic Scattering and Total Cross-Sections, Scaling and the Approach to Scaling, Diffraction Excitation, Two-Body Correlations and finally, Large Transverse Momentum Phenomena. Experimental results are only briefly presented. They are discussed from a theoretical point of view, with emphasis on the information they give, the questions they raise and the type of further experiments which they suggest.

The presentation tries to be self-contained. This paper, however, does not go into technical points and does not describe detailed model calculations. They are only referred to.

Lecture Notes : 1973 CERN/JINR School of Physics, Ebeltoft, Denmark.

1973 Summer Institute on Particle Interactions at Very High Energies, Louvain, Belgium.

This article is also appearing at part of the proceedings of the CERN/OINR School of Physics, published as a Cern Yellow report.

Keywords

Transverse Momentum Rapidity Distribution Rapidity Interval Inclusive Distribution Pion Yield 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References and Notes

  1. 1).
    Experiments at ISR have been so far performed with coasting beams of 11, 15, 22, 26 and 31 GeV/c, respectively. The highest energy requires acceleration in the storage rings proper. These beam energies span a range extending from 250 to 2000 GeV, when expressed in terms of stationary target experimentation. It will be referred throughout as the ISR energy range. Beam-beam collisions with beams of different momenta allow to reach intermediate centre-of-mass energies.Google Scholar
  2. 2).
    At present the luminosity reaches the value L = 4.4x1030cm-2 sec-1. It is obtained with coasting beams of 11–12 A each. The interaction rate of a reaction is obtained multiplying the luminosity by the cross-section. With a total cross-section of 40 mb we obtain about 2x105 event/sec and correspon¬dingly about 2x106 charged secondary particles/sec on each intersection.Google Scholar
  3. 3).
    For a detailed review of the features and performances of the machine, see, K. Johnsen, Instruments and Methods 108, 205 (1973).CrossRefGoogle Scholar
  4. 4).
    Lepton physics at the ISR (single electron or muon distributions probing for W, or dilepton search probing for heavy photon and more generally for any weak interaction effect) has so far met with negative results only. Improvements in machine luminosity, detector solid angle and efficiency should eventual¬ly allow for a much more detailed search than so far possible. In any case, this review limits itself to hadronic phenomena only.Google Scholar
  5. 5).
    U. Amaldi et al., Phys. Letters 44B, 112 (1973);CrossRefGoogle Scholar
  6. U. Amaldi, Erice Lecture Notes (1973);Google Scholar
  7. S.R. Amendolia et al., Phys. Letters 44B, 119 (1973); Nuovo Cimento to be published;Google Scholar
  8. G. Belletini, Rencontres de Moriond. (1973).Google Scholar
  9. 6).
    G. Giacomelli, Rapporteur’s talk, proceedings of the Batavia-Chicago Conference, Vol. 3, 219 (1973), edited by J.D. Jackson and A. Roberts.Google Scholar
  10. 7).
    For a review of the implications of unitarity, causality used together with extremely general properties such as the short-range nature of strong interactions, see S.M. Roy, Physics Reports 5C, 1125 (1972). This includes the well-known Froissart bound according to which a(E) cannot rise faster than log2E, asymptotically.Google Scholar
  11. 8).
    Explicit models actually meet the Froissart bound. This is in particular the case of the Cheng and Wu model. H. Cheng and T.T. Wu, Phys. Rev. Letters 24, 1456 (1970) and related papers. The model is based on an electrodynamic analogy. For a detailed fit, see, H. Cheng, J. Walker and T.T. Wu, to be published.Google Scholar
  12. 9).
    This is most generally expected in the framework of the Gribov Reggeon calculus. See: A. Tavkhelidze, Rapporteur’s talk, Kiev Conference (1971); K.A. Ter Martirosyan, JETP 11, 45 (1970).Google Scholar
  13. 10).
    We will refer to as NAL energies the 100–400 GeV energy range.Google Scholar
  14. 11).
    J. Benecke; T.T. Chan, C.N. Yang and E. Yen, Phys. Rev. 188, 159 ( 1969 ); C.N. Yang, “High Energy Collisions”, Gordon and Breach Publ., New York (1969).Google Scholar
  15. 12).
    R.P. Feynman, Phys. Rev. Letters 23, 1415 (1969) and “High Energy Collisions”, cp. cit.Google Scholar
  16. 13).
    K. Wilson, Acta Physica Austriaca 17, 37 (1963).Google Scholar
  17. 14).
    A.H. Mueller, Phys. Rev. D2, 2963 (1970). This is being discus¬sed by K. Kajantie and by R. Muradyan, Ebeltoft School Pro¬ceedings.Google Scholar
  18. 15).
    The elastic cross-section is 20% of the total cross-section and single diffractive excitation corresponds to a cross-section about as large as ael. But probably a little smaller.Google Scholar
  19. 16).
    A. Wroblewski, Rapporteur’s talk, Kiev Conference (1970);Google Scholar
  20. M. Deutschmann, Rapporteur’s talk, Amsterdam Conference (1971); H. Satz, ibid;Google Scholar
  21. M. Jacob, Rapporteur’s talk, Batavia-Chicago Conference (1972);Google Scholar
  22. D.R.O. Morrison, Proceedings of the Oxford Conference (1972);Google Scholar
  23. H.M. Chan, ibid., and CERN School (1972);Google Scholar
  24. J. Sens, Proceedings of the Oxford Confernece (1972), and meeting of the New York Academy of Sciences (1973).Google Scholar
  25. 17).
    L. Van Hove, Physics Reports 1C, 347 (1971);CrossRefGoogle Scholar
  26. D. Horn, Physics Reports 4C, 1 (1972);CrossRefGoogle Scholar
  27. W.R. Frazer et al., Revs. Modern Phys. 44, 284 (1972).CrossRefGoogle Scholar
  28. F.L. Feinberg, Physics Reports 5C, 237 (1972);CrossRefGoogle Scholar
  29. For a summary of the present review, one may see:Google Scholar
  30. M. Jacob, Physics at the ISR, a Review of Recent Results, CERN preprint TH. 1639 (1973). “Feldo and quanta”, to be published the key features of the multi-exchange picture often quoted here should be traced back to D. Amati et al, Nuovo Cimento 26, 896 (1962).CrossRefGoogle Scholar
  31. 18).
    The topics covered have been the following: Correlation at wide angle 1; large transverse momentum phenomena 2; scaling and the approach to scaling 3; two-body correlations and associated multiplicity 4; diffraction excitation 5; elastic scattering and total cross-section 6.Google Scholar
  32. 19).
    As a tentative guide to the partly preprint literature which is available, as well as to forthcoming publications; one may list under each topics the ISR collaborations which have relevant data in final or preliminary form. They should be contracted for further information when it is available. The acrostics thus introduced will be used throughout. Elastic scattering and total cross-section (Section 2) CERN-Rome (CR), Pisa-Stony Brook (PSB), Aachen-CERN Genova-Harvard-Turino (ACGHT). Scaling and the approach to scaling (Section 3) CERN-Holland-Lancaster-Manchester (CHLM), CERN-Bologna (formally including Argone) (CB), PSB, ACGHT, Saclay Strasbourg (SS), British-Scandinavian (BS), the latter two at wide angle (slow centre-of-mass secondaries). Diffractive excitation (Section 4) CHLM, ACGHT, PSB. Correlations (Section 5) PSB, CERN-Hamburg-Vienna (CHV), CHLM, CERN-Columbia¬Rockefeller (CCR), the latter one in connection with large pT secondaries. Large transverse momentum phenomena (Section 6) CCR, SS, BS, PSB.Google Scholar
  33. 20).
    This corresponds to an isotropic decay of the cluster, with associated multiplicity increasing linearly with the cluster mass M (fixed and#x003C;pTand#x003E;). However, if one associates the cluster with the decay products of an excited hadron, this primary state should generally be produced in an aligned configuration with high spin (high mass) and low helicity. The corresponding secondaries should then show an asymmetry resulting from an¬gular momentum conservation with and#x003C;pLand#x003E; and#x003E; and#x003C;pTand#x003E; when both are measured in the cluster rest frame. The rapidity domain on which the decay products are expected to scatter will there¬fore increase with increasing mass. As a result, the associa¬ted multiplicity will increase more slowly than linearly with M at large M. Our choice of two units for the minimal cluster size is therefore a very conservative one. It maximizes the secondary density.Google Scholar
  34. 21).
    This has not been possible so far. The split field magnet facility which is being installed on one of the intersection regions should allow such a type of analysis for the first time.Google Scholar
  35. 22).
    NAL-ANL Collaboration. J. Whitmore, private communication, and invited paper Vanderbilt Conference (1973).Google Scholar
  36. 23).
    G. Barbiellini et al. (ACGHT), Phys. Letters B39, 663 (1972);CrossRefGoogle Scholar
  37. G. Barbiellini B35, 355, 361 (1971). See also, G. Giacomelli, Ref. 6 ).Google Scholar
  38. 24).
    V. Bartenev et al., Phys. Rev. Letters 29, 1755 (1972);CrossRefGoogle Scholar
  39. R.L. Cool, Proceedings of the Royal Society, to be published (1973).Google Scholar
  40. 25).
    G.G. Beznogikh at al., Phys. Letters 30B, 274 (1969)Google Scholar
  41. JINR preprint E1–6615 (1972).Google Scholar
  42. 26).
    U. Amaldi et al., Phys. Letters 43E, 231 (1973); 36B, 504 (1971).Google Scholar
  43. 27).
    The exponential fit to the low It! data neglects any spin flip effects. They are thus assumed to be negligible but a more detailed analysis should also introduce them. Recent fits also assume that p does not vary appreciably with t in the interference range. For Coulomb effect, consult: B. West and D.R. Yennie, Phys. Rev. 172, 1413 (1968).Google Scholar
  44. 28).
    A. Wu Chao and C.N. Yang, Stony Brook preprint (1973);Google Scholar
  45. T.T. Chou and C.N. Yang, Phys. Rev. 170, 1591 (1968).CrossRefGoogle Scholar
  46. 29).
    This minimum is very different in nature from those observed at typical PS energies in Grp or K-p scattering and which are associated with the interference of secondary Regge tra¬jectory exchange. In pp (and Op) scattering, a featureless diffractive peak should develop a minimum with increasing energy, whereas in 7-p (and K-p) scattering the clear minimum at t=-0.6 seen as PS energy should first gradually disappear, while a diffraction minimum at higher It! would appear.Google Scholar
  47. 30).
    The first zero of the amplitude is then put in correspondence with the first zero of J1 (RA). (One has to integrate over the nonflip eikonal amplitudes which are proportional to Jo(rVTt).) We are therefore facing a typical distance of 0.5 fermi.Google Scholar
  48. 31).
    K. Kajantie, Proceedings of the CERN-JINR School (1973). For a review of Regge models and duality, see, M. Jacob, Brandeis Lecture Notes (1970), Vol. II.Google Scholar
  49. 32).
    N.N. Khuri and T. Kinoshita, Phys. Rev. 1376, 720 (1965).CrossRefGoogle Scholar
  50. 33).
    For a comprehensive review of present key questions, see: A. Martin, Proceedings of the Royal Society, to be published (1973), CERN preprint TH. 1650 (1973).Google Scholar
  51. 34).
    J. Fischer and C. Bourrely, CERN preprint TH. 1652 (1973). J. Diddens and W. Bartel, CERN preprint NP (1973).Google Scholar
  52. 35).
    In terms of J plane singularity a loges increase of atot corresponds to a branch point at J=1 with a higher singulari¬ty tan a pole ((J-1)2 corresponds to log s ...). A (log s)-1 approach to an asymptotic value is generally associated with a logarithmic branch point at J=1. See, F. Zachariasen, Models with growing cross-sections, Caltech preprint (1973).Google Scholar
  53. 36).
    A behaviour of the type imposed by a fixed pole and its shiel¬ding cut deviced in order to avoid the Gribov paradox would also give a rising cross-section (for a while) and a slope parameter approaching a constant. The question of fixed pole has been discussed by R. Oehme.Google Scholar
  54. 37).
    R.J. Eden, Phys. Rev. Letters 16, 39 (1966);CrossRefGoogle Scholar
  55. T. Kinoshita, Perspectives in Modern Physics, Interscience Publ. New York (1966).Google Scholar
  56. 38).
    L. Lukaszuk and A. Martin, Nuovo Cimento 52A, 122 (1966).Google Scholar
  57. 39).
    J. Whitmore, Invited paper, Vanderbilt Conference (1973), and references therein.Google Scholar
  58. The Brookhaven energy results are from R. Panvini et al. For a review of the NAL track chamber results, see:Google Scholar
  59. J. Whitmore, Physics Reports, in preparation.Google Scholar
  60. 40).
    S. Fubini, Scottish Universities Summer School (1963), and references therein.Google Scholar
  61. F. Zachariasen and G. Zweig, Phys. Rev. 160, 1322, 1326 (1967). For a review:Google Scholar
  62. M. Jacob, Les Houches Lecture Notes (1971).Google Scholar
  63. 41).
    F.Zachariasen, Physics Reports 2C, 1 (1971), and references therein.Google Scholar
  64. 42).
    Even at ISR we may casually speak about beam and target par¬ticles even though the situation is experimentally symmetri¬cal (it is always the case in the cetnre-of-mass system). With rapidity distribution switching from the laboratory to the centre-of-mass system amounts merely to a translation.Google Scholar
  65. 43).
    A.H. Mueller, Proceedings of the Batavia-Chicago Conference (1972);Google Scholar
  66. Ed. Berger et al., Phys. Rev. D9, 2580 (1972).Google Scholar
  67. 44).
    The same applies to statistical and thermodynamical models. They give scaling distribution for the very same reason. For a review: K. Gottfried, CERN Academic Training Lectures (1973).Google Scholar
  68. 45).
    T.T. Chou and C.N. Yang, Phys. Rev. Letters 25, 1072 (1970);CrossRefGoogle Scholar
  69. For a review: L. Caneschi, Ref. 18. 3 ).Google Scholar
  70. CHLM Collaboration, J. Albrow et al., Nuclear Phys. 51B, 388 (1973);Google Scholar
  71. CHLM Collaboration, J. Albrow et al., Phys. Letters 44B, 207 (1973)Google Scholar
  72. CHLM Collaboration, J. Albrow et al., 44B, 518 (1973).Google Scholar
  73. The last papers contain data relevant to Section 5. CHLMGoogle Scholar
  74. Preprints (1973).Google Scholar
  75. CB Collaboration, A. Bertin et al., Phys. Letters 41B, 201 (1972). CB Preprints (1973).Google Scholar
  76. 48).
    R.J. Eden, P.V. Landshoff, D.I. Olive and J.C. Polkinghorne, “The Analytic S Matrix”, Cambridge (1966).Google Scholar
  77. 49).
    A leading Pomeranchon trajectory with intercept one gives constant cross-section asymptotically. Scaling cannot there¬fore be considered as a priori more reliable than the appro¬ximation of a constant cross-section which remains a good approximation (10%) on a tremendous energy range 20–2000 GeV ! It is the more so impressive that most partial cross-sections for exclusive channels show strong variations with energy. f/a could still reach a limiting value but there is at pre¬sent no compelling theoretical reasons for it if a rises. The behaviour of multiplicity distributions will not be discussed here. See Refs 17), 18) and 19) and in particularGoogle Scholar
  78. Z. Koba, Ebeltoft Proceedings (1973). Section 5 can be con¬sidered as an introduction to Koba’s lectures.Google Scholar
  79. 50).
    M. Jacob and R. Slansky, Phys. Rev. D5, 1847 (1972);Google Scholar
  80. M. Jacob, R. Slansky and C. Wu, Phys. Rev. 09, 2444 (1972).Google Scholar
  81. 51).
    M. Jacob, Invited paper, Argonne Conference (1972).Google Scholar
  82. 52).
    M. Einhorn, Contribution to the Batavia-Chicago Conference (1972).Google Scholar
  83. 53).
    An isolated pole at 3=1 is only an approximation. One may well try to test scaling or factorization to better than 10% but one should not be surprised if they fail at such an accuracy level. A 10% accuracy over such a wide energy range remains impressive.Google Scholar
  84. Saclay-Strasbourg Collaboration, M. Banner et al. Phys. Letters 41E, 547 (1972);Google Scholar
  85. Saclay-Strasbourg Collaboration, M. Banner et al. Phys. Letters 44B, 537 (1973). SS Preprints (1973).Google Scholar
  86. 55).
    For a review of fragmentation models, see Refs. 17), 18), and: J.M. Wang, Zakopane Conference (1972);Google Scholar
  87. Ed. Berger, Oxford Conference (1972).Google Scholar
  88. The empirical validity of the key assumptions on an extended though limited energy range is discussed in Ref. 50).Google Scholar
  89. 56).
    A fragmentation model in its most simple form, namely isotro¬pic decay of excited hadronic states with constant production cross-section is now certainly incorrect. It does not mean though that it cannot be used to parametrize reasonably well important effects and thus achieve some predictive value. To the extent that its including leading particle effects gives a good description of the initial rise of higher multiplicity cross-sections with increasing energy and to the extent that their eventual decrease is not obvious experimentally until one reaches at least 100 GeV, it could thus be used at predic¬ting (see Refs. 43) and 50)) correctly the rise of the inclu¬sive distribution at x=0 (almost a factor 2 from PS to NAL energies) and the widening of the multiplicity distribution (important rise of f2 from PS to NAL energies). The corres¬ponding approximations can a posteriori be introduced in a multiperipheral calculation which, provided it also includes some clustering among slow centre-of-mass secondaries, is certainly more amenable to the description of the observed effects at ISR energies. However, as stressed in Ref. 50), a rapidity interval of 4, as available at PS energy is not enough to see anything but simple fragmentation at the single and even two particle level.Google Scholar
  90. 57).
    British-Scandinavian Collaboration, H. Boggild et al., Pre¬prints (1973).Google Scholar
  91. 58).
    P. Carruthers, Cornell Preprints (1973).Google Scholar
  92. 59).
    R. Slansky, Invited paper, Meeting of the New York Academy of Sciences (1973), and Physics Reports, in preparation. Clustering effects have been extensively discussed phenomeno¬logically by Ed. Berger and G. Fox, Preprints ( 1972, 73 ).Google Scholar
  93. 60).
    L. Van Hove, Ref. 17), and F. Zachariasen, Ref. 41). See also, L. Van Hove, Ref. 18. 5 ).Google Scholar
  94. 61).
    For any particular excitation mass, one thus minimizes momen¬tum transfer and maximizes the rapidity gap between the quasi-elastically scattered proton and the remainder secondaries. This enforces the Pomeranchon exchange approximation (diffrac¬tion) in the production amplitude.Google Scholar
  95. 62).
    R. Slansky, Invited paper APS Meeting, Washington (1972). With wider acceptance small angle sectrometers or the SFM, one will also be able to study double excitation, looking at a forward well-isolated pTr+7r-system. A detailed analysis of A++ production is the first experimental step (ACGHT-UCLA).Google Scholar
  96. 63).
    For obvious geometrical reasons such distributions could not yet be obtained at very low It or pT, when it would be extremely interesting to have the corresponding data. Experi¬mentation with unequal momenta should help (CHLM) with present angular limitations.Google Scholar
  97. 64).
    Such a statement should be supported by a better resolution. It is very important to know whether those resonances which are diffractively produced at PS energies are still produced with similar cross-sections at ISR energies. The first N# are all dumped into the first bin in Fig. 13a. Study of exclusive channels in the SFM will be very interesting (CHOV and Prince¬ton-Pavia).Google Scholar
  98. 65).
    H. Abarbanel et al., Phys. Rev. Letters 26, 937 (1971);CrossRefGoogle Scholar
  99. R.D. Peccei et al., Phys. Rev. Letters 26, 1076 (1971);CrossRefGoogle Scholar
  100. P. Chliapnikov et al., Phys. Letters 35B, 581 (1971).Google Scholar
  101. 66).
    P.V. Landshoff and J.C. Polkinghorne, Physics Reports 5C, 1 (1972); C. De Tar, Physics Reports, in preparation;Google Scholar
  102. S.D. Ellis et al., Phys. Rev. D6, 1347 (1972);Google Scholar
  103. A.B. Kaidalov et al., Leningrad Preprint (1973).Google Scholar
  104. 67).
    F. Sannes et al., Rutgers Preprint (1973), and Vanderbilt Conference (1973);Google Scholar
  105. R. Pagnamenta, private communication.Google Scholar
  106. One finds a similar approach to scaling in the fragmentation region (x=0.8) and in the “dip” at x = 0.9 between the fall of the fragmentation component and the rise of the quasi-elastic contribution.Google Scholar
  107. 68).
    F.T. Dao et al., Contribution to the APS meeting, New York and Vanderbilt Conference (1973);Google Scholar
  108. P. Schlein, to be published, and Ref. 18.5).Google Scholar
  109. 69).
    The absolute value of the associated multiplicity should probably be further corrected for electron contamination (the quoted results are preliminary). The relative values are, however, meaningful and most valuable.Google Scholar
  110. 70).
    The features mentioned here still correspond to very preli¬minary results, Refs. 18.4). They are listed as provocative statements for a more extensive analysis. The Pisa-Stony¬Brook Collaboration should be consulted for any more detailed information.Google Scholar
  111. 71).
    See proposals form the Princeton-Pavia and CERN-Hamburg-Orsay¬Vienna Collaborations: pp - pp7+r-and pp7+Tr-e7- reactions.Google Scholar
  112. 72).
    C. Quigg, Invited talk, Vanderbilt Conference (1973); A. Mueller, Summary of the Discussion Session on ParticleGoogle Scholar
  113. Production, Chicago-Batavia Conference (1972); See also Ref. 18) (1 and 4).Google Scholar
  114. 73).
    This is done for one further, temporary reason. Observing charged secondaries, it is still difficult to separate actual pions from the electrons which they knock off the walls. This increases the single aprticle yield by a spurious factor which should cancel out, however, to a large extent, in (5.3). The observed secondaries are far apart enough so that one may consider globally each pion with its “associated” electrons, without being fooled by pion-electron correlations (cross talk between counters).Google Scholar
  115. 74).
    K. Wilson, Cornell Preprint (1971);Google Scholar
  116. R. Arnold, Argonne Preprints (1972);Google Scholar
  117. R. Arnold and D. Campbell, Revs. Modern Phys., to be published.Google Scholar
  118. CHV Collaboration, K. Winter et al. Preprint (1973). See also Ref. 18.4).Google Scholar
  119. 76).
    Z. Koba, CERN-JINR School lecture notes (1973). See also Ref. 16) (Batavia Conference), and Ref. 72 ). J.D. Jackson, Invited paper Vanderbilt Conference (1973).Google Scholar
  120. 77).
    For the detailed analysis of correlation in a multiperipheral and diffraction model, see:Google Scholar
  121. W. Frazer, La Jolla Preprints (1973).Google Scholar
  122. 78).
    J. Finkelstein, Columbia Preprint (1973); J. Ellis, J. Finkelstein and R. Peccei, SLAC Preprint (1972).Google Scholar
  123. 79).
    This point of view has been emphasized in:Google Scholar
  124. M. Jacob, “Two Topical Questions at ISR Energy”, Comments, to be published (1973).Google Scholar
  125. 80).
    The CERN-Munich streamer chamber and the BS-Orsay-MIT, SFM experiment should clarify these questions.Google Scholar
  126. 81).
    One should not undermine the fact that at present the best reliable correlation data show an increase of the single par¬ticle yield (inclusive distribution) which is much more than what is reported by experiments using spectrometers (BS and SS). As already discussed, the observed multiplicity is pro¬bably too high. However, such effects disappear to a large extent when one calculates R. Focusing on R, discrepancies notwithstanding, is probably the correct attitude to follow and this is what is done here anyway. Nevertheless, one cannot consider the situation as satisfactorily settled before correlations are measured in experiments which fully agree with single arm spectrometer results. The same remark applies to the data shown in Fig. 21b. The magnificent sca¬ling seen in the central region should be considered keeping in mind the much different behaviour found in the typical fragmentation region. As illustrated by Fig. 19, limiting fragmentation should be a reliable picture and a simple relation among the distributions should be found.Google Scholar
  127. 82).
    One should keep in mind that, within the same approximation, ael vanishes asymptotically.Google Scholar
  128. 83).
    Such a behaviour is quite compatible with the data shown in Fig. 21. However, as discussed in Section 5d, one should not already conclude that an expected Regge behaviour has been found. The Mueller formalism is indeed not very well suited to small Ay where the approximation of a leading secondary trajectory disappears. See Ref. 72).Google Scholar
  129. 84).
    In a multiexchange model, this would correspond to a large rapidity gap (lyC-y0l » 1), hence to a good Reggeon exchange approximation. We may therefore consider this as a dual effect.Google Scholar
  130. 85).
    M. Jacob and J. Weyers, Nuovo Cimento 70, 285 (1970).CrossRefGoogle Scholar
  131. 86).
    A 90° double arm spectrometer experiment is now set up (SS¬CCR).Google Scholar
  132. 87).
    P. Pirilä and S. Pokorski, CERN Preprints (1972, 1973). See also:Google Scholar
  133. A. Morel and F. Hayot, Saclay Preprint (1973);Google Scholar
  134. W. Schmidt Parzefall, Preprint (1973).Google Scholar
  135. 88).
    J.D. Jackson and C. Quigg, NAL Preprint (1972), and Ref. 77);Google Scholar
  136. F. Fialkowski and H.I. Miettinen, Phys. Letters 43B, 61 (1973);CrossRefGoogle Scholar
  137. L. Van Hove, Phys. Letters 43B, 65 (1973);CrossRefGoogle Scholar
  138. H. Harari et al., Phys. Letters 43B, 49 (1973).CrossRefGoogle Scholar
  139. 89).
    The pl. correlation at small x appears to be particularly strong. Even though the proton yield is small, pr correlations may not be negligible among charged-charged correlations at wide angle. There is a great interest in the study of those cases where the proton is produced with x=0 and in particular since the pp ratio is still 2. Results from the SFM, the SS double arm spectrometer and NAL should be interesting in that respect. In words, it would be important to know how a nucleon can be practically “brought to rest” in an ISR collision.Google Scholar
  140. 90).
    Correlation results such as those seen in Fig. 21 are then interpreted as the sum of two terms. One distinguishes a flat top contribution (at the 30% level, say) corresponding to long-range effects and extending over the rapidity plateau (about 4 units across) and a slightly narrower short-range effect (2 to 3 units across) which is associated with the clustering among pions proper. One may then not yet attach too much importance to the actual shape of R even though it matches what is predicted in the Mueller formalism which would asymptotically include short-range effects only. With increasing energy, one may expect short-range and long-range effects to show different specific width (a 3 unit width spike on a flat plateau, say). It is an amusing feature that ISR energies are such that the two effects match so well to each other. See also Ref. 72). As stressed in Ref. 79), separating the two effects requires a model calculation. Which belongs to which exactly is still an open question.Google Scholar
  141. 91).
    G. Giacomelli, CB Collaboration, private communication.Google Scholar
  142. 92).
    See Refs. 18) and 19) (CB, BS, SS and CHLM).Google Scholar
  143. 93).
    It is even remarkable that the pT distribution varies so weakly even as one goes from fragmentation pions to pioni¬zation pions or as one considers it for different multipli¬cities. The proton pT distribution could a priori show a stronger variation, slowly increasing with multiplicity at any given energy.Google Scholar
  144. 94).
    F. Gilman, Physics Reports 4C, 95 (1972).CrossRefGoogle Scholar
  145. 95).
    S. Berman, J. Bjorken and J. Kogut, Phys. Rev. 04, 3388 (1971);Google Scholar
  146. J. Kogut and D. Susskind, Physics Reports, to be published.Google Scholar
  147. 96).
    F. Low and S. Treiman, Phys. Rev. D5, 756 (1972).Google Scholar
  148. 97).
    See Refs. 18) and 19) (CCR). With an increase in luminosity which can be rightfully expected or (and) an increase in detection efficiency (large solid angle detector) lepton search should be eventually successful. The question of neutral currents gives an extraordinary interest to lepton pair search.Google Scholar
  149. 98).
    Data on large transverse momentum phenomena (inclusive yields) have been obtained by the CCR, SS and BS Collaborations. They were first presented at the Batavia Conference. For a com¬prehensive review, see Ref. 18. 2 ).Google Scholar
  150. 99).
    B.J. Blumenfeld et al., Contribution to the APS Meeting, New York (1973).Google Scholar
  151. 100).
    M. Banner et al., Phys. Letters 44B, 537 (1973); Ref. 18.4) and SS Preprints (1973).Google Scholar
  152. 101).
    The lack of scaling of the large transverse momentum Tr° distribution reported by the CCR Collaboration at the Batavia Conference would exaggerate somewhat the actual effect. As discussed in Ref. 99), the trigger then used in this experi¬ment cannot be considered as actually inclusive. Requiring fast particles on both sides is a bias against events with large transverse momentum secondaries and the more so the lower the energy is. The SS Collaobration (Fig. 24b) used no extra trigger since its set-up was much less sensitive to background beam gas collisions.Google Scholar
  153. 102).
    M. Jacob, “The Question of Early Scaling”, Argonne Conference (1972).Google Scholar
  154. 103).
    T.T. Wu and C.N. Yang, Phys. Rev. 137, B708 (1965); H. Abarbanel et al., Phys. Rev. Letters 20, 280 (1968); Phys. Rev. 177, 2458 (1969).Google Scholar
  155. 104).
    M. Jacob and S. Berman, Phys. Rev. Letters 25, 1683 (1970).CrossRefGoogle Scholar
  156. 105).
    For a review of the parton picture, see: R.P. Feynman, Benjamin Lecture series (1973);Google Scholar
  157. J. Kogut and D. Susskind, Physics Reports, to be published; V. Matveev, Ebeltoft Proceedings (1973), and references therein.Google Scholar
  158. 106).
    The low pT component would be due to outer meson cloud effects (this of course includes resonance formation and multi-Reggeon exchange), while the large pT component would correspond to the inner (practically pointlike) structure apparently present within the proton. As already stressed there is, however, no clear cut separation between two compo¬nents.Google Scholar
  159. 107).
    P.V. Landshoff and J. Polkinghorne, Cambridge DAMTP Preprints (1972 and 1973 ).Google Scholar
  160. 108).
    R. Blankenbecler et al., Phys. Letters 42B, 461 (1972); SLAG Preprints (1972 and 1973 ).Google Scholar
  161. 109).
    A large transverse momentum secondary is now required as a trigger in several recent proposals (SS-CCR, CERN-Munich Streamer Chamber and CERN-Munich SFM).Google Scholar
  162. 110).
    In the rest frame of particle B, y is the energy received times twice mB when A scatters into C.Google Scholar
  163. 111).
    D. Amati, L. Caneschi and M. Testa, CERN Preprint (1972).Google Scholar
  164. 112).
    We already emphasized the importance of threshold effects which should be mixed up with more interesting (partonlike) dynamical effects. This should be kept in mind when analyzing data in terms of a specific S dependence at fixed pT in order to determine n in (6.7). At present, one should probably put more weight on qualitative effect (charge effect, particle ratio, associated multiplicity) rather than on a specific fit to the inclusive distribution.Google Scholar
  165. 113).
    For a specific model calculation, see, for instance: Ed. Berger and D. Branson, CERN Preprint (1973).Google Scholar
  166. British-Scandinavian Collaboration, B. Alper et al., Phys. Letters 44B, 521, 527 (1973), and Preprints (1973); H. Boggild, Private communication.Google Scholar
  167. 115).
    One should watch out for new results from the BS and SS Collaborations.Google Scholar
  168. 116).
    It is definitely too early to report specific results. Ref. 18.4) can be consulted for more details. One should now watch out for new results from the PSB and CCR Collaboration but also from CERN-Munich.Google Scholar
  169. 117).
    At least two new experiments will use a large pTy as a trigger. The associated multiplicity will first be analyzed in the streamer chamber (CERN-Munich) and next in the split field magnet. A detailed picture should then be obtained through these “second generation” experiments. At the same time, observation of the large pT inclusive distribution at NAL, and later on, some detailed analysis of the correspon¬ding final states, will be very interesting.Google Scholar
  170. 118).
    CCR Collaboration, Proceedings of the Vanderbilt Conference (1973).Google Scholar
  171. 119).
    Separating arbitrarily as a “jet”, particles of similar rapi¬dities with 0.6 and#x003C; pT and#x003C; 6 GeV/c, say, one may expect a typical 0.4 GeV/c transverse momentum spread measured with respect to the mean jet direction. This gives a rather wide opening angle. A small aperture detector would therefore be too selective or too sensitive to large pT secondaries with simi¬lar momenta only. This may be a relative minority within the jetGoogle Scholar
  172. 120).
    J. Benecke et al., Nuovo Cimento A7, 311 (1972).CrossRefGoogle Scholar
  173. P. Carruthers, Physics Reports 1C, 1 (1971).CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1974

Authors and Affiliations

  • M. Jacob
    • 1
  1. 1.CERNGenevaFrance

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