Minijets as a further test of QCD

Perturbative QCD is shown to be in quantitative agreement with one-and two-jet production data in the range \(27 \lesssim \sqrt s \lesssim 900GeV\) GeV forP _T(jet)?5 GeV. The integrated jet yield above a fixedP _T(parton)?3 GeV accounts for the \(\bar pp\) inelastic cross section rise in the same range. QCD predictions for jet yields up to \(\sqrt s = 40TeV\) are presented and the role of non-perturbative corrections, ultimately saving unitarity, is briefly discussed.     

Mirror fermion production inep collisions

The phenomenology of mirror fermions is studied in a model with three heavy mirror fermion families. The tree unitarity bounds on the mirror masses are determined. The production cross-sections and decay characteristics of mirror fermions are calculated in high energy electron-proton collisions. For mirror mixing angles of the order of the present upper limits mirror fermion production at HERA ( \(\sqrt s = 314 GeV\) ) is observable up to masses near 200 GeV. For a possible HERA upgrade ( \(\sqrt s = 566 GeV\) ) this limit goes up to about 350 GeV and anep collider in the LEP tunnel ( \(\sqrt s = 1.4 TeV\) ) could cover the range below 500 GeV.     

Rules of thumb for theZ line shape

In this paper the theoretical parameters of theZ line shape, such asM _Z andΓ _Z, and the one photon exchange diagram are related to a set of parameters characterizing the experimental line shape. The latter are the peak height σ_max, peak position \(\sqrt {s_{\max } } \) and half peak positions \(\sqrt {s_ \pm } \) . The rules of thumb are accurate within 10 MeV. As a result we obtain approximate formulae which expressM _Z and Γ_Z in the measured \(\sqrt {s_{\max } } \) and \(\sqrt {s_ + } - \sqrt {s_ - } \) .     

Benchmark cross sections forp \bar p collisions at 1.8 TeV

High-energyp \(\bar p\) collisions provide many quantitative tests of the standard model. Of particular interest are “hard scattering” processes, which test not only standard model matrix elements and higher order perturbative corrections, but also the distributions of quarks and gluons in the colliding hadrons. We present detailed comparisons of data from the CERNSp \(\bar p\) S collider with theory, incorporating up-to-date parton distributions derived from recent deep inelastic scattering data. Encouraged by the excellent agreement between data and theory at \(\sqrt s \) =630GeV, we present a complete set of “benchmark” predictions for the FNALp \(\bar p\) collider at \(\sqrt s \) =1.8TeV.     

Gluino and squark search at Tevatron collider energies

Event rates and distributions for high mass gluinos and squarks are computed at Tevatron collider energies, imposing experimentally realisticP _T cuts. Gluino and squark masses can be probed up to 200 GeV at \(\sqrt s = 2 TeV\) , and up to about 150 GeV at \(\sqrt s = 1.6 TeV\) with the supersymmetric signal being much more enhanced relative to the standard model background than at CERN \(\bar p\) energies. If the CERN UA1 missing-p _T events are indeed indicative for the existence of gluinos and/or squarks with masses of about 50–70 GeV, then the Fermilab collider experiments should easily confirm the expected huge supersymmetric signals.     

Multiplicity dependence of the average transverse momentum and of the particle source size inp−p interactions at\sqrt s =62, 44 and 31 GeV

The average transverse momentum and the size of the particle emitting source (measured via Bose-Einstein correlations) have been studied as functions of the charged particle density in the central region inp-p interactions at \(\sqrt s \) =62, 44 and 31 GeV. Both the average transverse momentum and the source size increase with increasing density at all three energies. This effect, very weak at \(\sqrt s \) =31 GeV, becomes stronger with increasing energy.     

Crossing-odd effects in soft nucleon collisions

A complete set of the data onpp andp \(\bar p\) scattering including measurements in the Coulomb interference region are analised to discover crossingodd effects in soft collisions. It is shown that the odderon is unable to produce a significant increase in ReA/ImA at \(\sqrt s = 546\) GeV. Moreover, the data give preference to that odderon which makes negative contribution to Re \(A_{p\bar p} \) and ceases the decrease of difference inp \(\bar p\) andpp total cross-sections.     

\bar \Lambda Production inK − p interactions at 32 GeV/c

Antilambda production is studied inK ^? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep _⊥ ² distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)^?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK ^- p→Λ \(\bar \Lambda \) +X K ^- p→ \(\bar \Lambda \) K ⁿ +X, andK ^- p→ \(\bar \Lambda \) p+X.     

Very high energy nucleus-nucleus collisions and multi-chain model

Inclusive and semi-inclusive production of Λ and \(\bar \Lambda\) inK ⁺ p interactions is studied at an incident momentum of 70 GeV/c. Cross sections and single particle distributions are presented and compared with data at lower energies. Scaling is observed between 32 and 70 GeV/c in the Feynmanx variable in the target and the beam fragmentation regions for Λ and \(\bar \Lambda\) inclusive production respectively. An increase of Λ ( \(\bar \Lambda\) ) production is observed in the beam (target) fragmentation regions, whereas the data at 70 and 32 GeV/c are reasonably close in the central region. The dependence of the Λ( \(\bar \Lambda\) ) polarization as a function ofx is measured and found to be in general agreement with the results at 32 GeV/c. The (Λ \(\bar \Lambda\) ) pair production cross section increases significantly from 32 to 70 GeV/c. The Λ and \(\bar \Lambda\) production associated with an identified proton is also studied.     

Wino and zino production inp\bar p collisions: first order supersymmetric QCD corrections

We compute the first order supersymmetric QCD correction to wino \((\tilde W)\) and zino \((\tilde Z)\) production in \(p\bar p\) collisions via subprocesses involving two massless partons inside the nucleon or one massless parton and a massive SUSY parton (squark or gluino). The first order SQCD corrections to the rapidity dependence at CERN collider and Tevatron energies are found large (K～2). The rates are important (～10^?2 nb at \(\sqrt s = 630\) GeV and ～10^?1 nb at \(\sqrt s = 2\) TeV), as soon as the \((\tilde W)\) and \((\tilde Z)\) production by squarks is allowed. Transverse momentum distributions are also given and their shape is found very sensitive to the presence of SUSY partons inside the nucleon.     

Partition temperature and fireballs of hadron-proton collisions

A geometric property is considered to relate the impact parameterb ofhh collision at a given \(\sqrt s \) to the partition temperatureT _p of producedn _ch pions. It is based on the overlapping of two Lorentz contracted fireballs (FB) associated to the primary hadrons, as is described in the partition temperature model (PTM), assuming for the FB radiusR=r(3n _ch/2)^1/3. For \(\bar p\) p collisions at \(\sqrt s \) = 540 GeV analyzed by the authors of the PTM,r=0.70±0.03 fm consistent with the pion radius, the computedT _p agree with their results for variousn _ch. The energy dependence ofT _p for \(\bar p\) p from \(\sqrt s \) = 13.8 to 900 GeV is accounted for by assuming the FB velocity with respect to the c.m.s., to behave likepp, i.e., β _F =1?λ with λ=2 〈P _⊥〉/λ〈P _∥〉 and \(\bar b = 0.98fm\) . Remarks are made on the relationship betweenT _p and the conventional temperature determined by 〈P _⊥〉 in terms of the Lorentz factor of the FB.     

Neutral strange particle production in proton-proton collisions at\sqrt s = 63 GeV

The inclusive cross section for the production ofK _s ⁰ mesons, Λ and \(\bar \Lambda\) particles in proton-proton interactions at \(\sqrt s = 63\) GeV is presented. The produced particles have been detected in the full phase space. Behaviour of the longitudinal and transversal depandences of the cross sections are discussed. The total production cross sections for _s ⁰ mesons and Λ particles was determined to \(\sigma _{{\rm K}_S^0 } = (25.5 \pm 1.4)\) mb andσ _Λ =(7.8±1.2) mb respectively. A strong energy dependence of the production cross sections is observed.     

Comparison of strange antibaryon and strange meson production inK + p interactions at 32 GeV/c

New experimental results are presented on inclusive production properties of \(\bar \Sigma ^{ * + } \) (1385) and \(\bar \Sigma ^{ * + } \) (1385) inK ⁺ p interactions at 32 GeV/c. The analysis is based on significantly larger statistics than previously available. A comparison is also made of invariantx-distributions ofK ⁰/ \(\bar K^0 \) , \(\bar \Lambda \) and \(\bar \Xi ^ + \) and of \(\bar \Sigma ^{ * \pm } \) (1385) andK ^*+(892). These spectra exhibit regularities expected from the quark-recombination picture when it is assumed that the strange mesons and antibaryons are produced off the strange \(\bar s\) -valence-quark in the incidentK ⁺ meson. Transverse momentum distributions are also presented forK ^*+(892) and \(\bar \Sigma ^{ * \pm } \) (1385) and found to be very similar. The results on strange antibaryon average multiplicities disagree strongly with a recent version of the additive quark model.     

The(cc) - (\overline {cc} ) (diquark-antidiquark) states ine + e − annihilation

The mass spectrum and decay modes of the \((cc) - (\overline {cc} )\) states are estimated in a quark-gluon model. We argue that the peculiar resonance-like structures ofR(e ⁺ e ^? →hadrons) for \(\sqrt s = 6 - 7\) GeV may be due to production of theP-wave \((cc) - (\overline {cc} )\) states. They are predicted to lie in the range 6.4–6.8 GeV and mainly decay into charmend mesons.     

Open beauty production in high energy π−-tungsten interactions

We present a study of \(B\bar B\) meson pair production inπ ^? interactions at 140, 194 and 286 GeV incident pion energy. At 286 GeV, where we have the best statistics, we find a model-dependent \(B\bar B\) production cross-section \(\sigma _{BB} = 14_{ - 6}^{ + 7} nb/nucleon\) .     

Quark-diagram estimates ofCP violation in two-body baryonicB_d^0 - \bar B_d^0 decays

CP violation in partial-decay-rate asymmetries are examined for some two-body baryonic decays of \(B_d^0 - \bar B_d^0 \) system. We discuss two feasible experimental circumstances: the symmetrice ⁺ e ^? collisions (i) on theZ ⁰ resonance to produce incoherent \(B_d^0 \bar B_d^0 \) states, and (ii) just above the ?(4S) resonance to produceC=even \(B_d^0 \bar B_d^0 \) states. Using the quark-diagram scheme, we estimate the branching ratios of those decays, and the numbers ofb \(\bar b\) pairs needed for testing theCP-violating effects for 3σ signature. We find that the promising channels may beB _d ⁰ , \(\bar B_d^0 \to p\bar p\) , \(\Delta ^ + \bar \Delta ^ - \) , \(p\bar \Delta ^ - \) , \(\Delta ^ + \bar p\) , \(n\bar n\) , \(\Delta ^0 \bar \Delta ^0 \) , \(n\bar \Delta ^0 \) , \(\Delta ^0 \bar n\) , \(\Sigma _c^ + \bar \Sigma _c^ - \) , \(\Lambda _c^ + \bar \Lambda _c^ - \) , \(\Sigma _c^ + \bar \Lambda _c^ - \) , \(\Lambda _c^ + \bar \Sigma _c^ - \) , \(\Sigma _c^0 \bar \Sigma _c^0 \) , \(\Xi _c^0 \bar \Xi _c^0 \) , which should be interesting for experimental observation.     

Inclusive production of neutral strange particles in\bar pp interactions at 70 GeV/c

The inclusive production ofK _s ⁰ , Λ and \(\bar \Lambda \) particles is investigated in 70 GeV/c \(\bar pp\) interactions in an experiment performed at CERN using BEBC equipped with a TST. Differential cross-sections are studied and compared with corresponding data at surrounding energies. Differences withpp data obtained at the same energy allow an estimate of theK _s ⁰ , production cross-section in annihilation processes. Evidence is also given for central \(\Lambda \bar \Lambda \) production.     

Reggeon calculus at collider energies

The phenomenology of the perturbative reggeon calculus at collider energies is studied. It is found that the graphs which were neglected at ISR energies are still negligeable at \(\sqrt s = 540 GeV\) . The pertubative series for the total cross section still converges reasonably fast. The values of the different parameters which describe rightly the data up to ISR energies give rise to a total cross section of around 60 mb at \(\sqrt s = 540 GeV\) . For these values, the corresponding low mass and high mass eikonal series converges much more slowly. The non perturbative reggeon calculus gives rise to a total cross section less than 60 mb.     

Indecomposable representations with invariant inner product

Consequences of the existence of an invariant (necessarily indefinite) non-degenerate inner product for an indecomposable representation π of a groupG on a space \(\mathfrak{H}\) are studied. If π has an irreducible subrepresentation π₁ on a subspace \(\mathfrak{H}_1 \) , it is shown that there exists an invariant subspace \(\mathfrak{H}_2 \) of \(\mathfrak{H}\) containing \(\mathfrak{H}_1 \) and satisfying the following conditions: (1) the representation π ₁ ^# =π mod \(\mathfrak{H}_2 \) on \(\mathfrak{H}\) mod \(\mathfrak{H}_2 \) is conjugate to the representation (π₁, \(\mathfrak{H}_1 \) ), (2) \(\mathfrak{H}_1 \) is a null space for the inner product, and (3) the induced inner product on \(\mathfrak{H}_2 \) mod \(\mathfrak{H}_1 \) is non-degenerate and invariant for the representation $$\pi _2 = (\pi _2 |_{\mathfrak{H}_2 } )\bmod \mathfrak{H}_1 ,$$ a special example being the Gupta-Bleuler triplet for the one-particle space of the free classical electromagnetic field with \(\mathfrak{H}_1 \) =space of longitudinal photons and \(\mathfrak{H}_2 \) =the space defined by the subsidiary condition.