Binary reactions in $$\bar pp$$ collisions at intermediate energies

We discuss here the binary reactions of strange and charmed particle production in collisions at intermediate energies. In the case of baryon production with only one strange or charmed quark the cross section is determined by planar diagrams withK ^*,K ^** orD ^*,D ^**-meson poles in thet-channel. We calculated these diagrams in the frame of quark-gluon string model (QGSM) proposed earlier. We obtained also the cross-sections for reactions with baryon exchange in thet-channel with and pair in the final state. Predicted cross-sections for the reactions of production are of the order of hundred nanobarns. Using reggeon calculus we estimated cross-sections of binary reactions with two or three strange quarks in the final state: and . We discuss also the possible manifestation of color transparency effects in reactions with antiprotons on nuclei where all antiproton quarks annihilate.     

Partition temperatures ofK 0 andΛ 0 fromπ + p collisions

The rapidity distributions of inclusive ⁺ p ^–,K ⁰, ⁰ andK ^* (892) atP _1ab=16 GeV/c of CERN experiments, are analyzed using the covariant partition temperatureT _p model. In the fireball system, apart fromK ^* (892),T _p ^* m, no indication of thermal equilibrium, the average momentum ofK ⁰ and ⁰ being approximately equal and in the opposite direction, the entropy density is practically the same forK ⁰ and ⁰ but less than that of ^–. It is found that the principle of equipartition holds rather for the momenta of ,K, and in the fireball system.     

Contributions toΛ c + →πΣ,πΛ andp\bar K^0 from excited states

We consider contributions to _c ⁺ , and from excited states. The calculations are performed within the MIT-bag model and a heavy quark bag model. Because the mass of _c ⁺ is rather big compared to the strange baryons, excited baryon states with mass close to that of _c ⁺ in some cases give significant pole contributions to the decay amplitudes of _c ⁺ .     

Understanding the scalar mesonq\bar q nonet

It is shown that one can fit the available data on thea _o(980),f _o(1300) andK _o ^* (1430) mesons as a distorted 0⁺⁺ nonet using very few (5–6) parameters and an improved version of the unitarized quark model. This includes all light two-pseudoscalar thresholds, constraints from Adler zeroes, flavour symmetric couplings, unitarity and physically acceptable analyticity. The parameters include a bare or mass, an over-all coupling constant, a cutoff and a strange quark mass of 100 MeV, which is in accord with expectations from the quark model. It is found that in particular for thea ₀(980) andf ₀(980) the component, in the wave function is large, i.e., for a large fraction of the time the state is transformed into a virtual pair. This component, together with a similar component of for thea ₀(980), and , and components for thef ₀(980), causes the substantial shift to a lower mass than what is naively expected from the component alone. Mass, width and mixing parameters, including sheet and pole positions, of the four resonances are given, with a detailed pedagogical discussion of their meaning.     

From the deuteron to deusons,an analysis of deuteronlike meson-meson bound states

A systematic study of possible deuteronlike twomeson bound states,deusons, is presented. Previous arguments that many such bound states may exist are elaborated with detailed arguments and numerical calculations including, in particular, the tensor potential. This tensor potential which is crucial for the deuteron binding is shown to be very important also in the mesonic case. Especially, in the pseudoscalar³ P ₀ pseudoscalar-vector and vector-vector channels the important observation is made that the centrifugal barrier from theP-wave can be overcome by the 1/r ² and 1/r ³ terms of the tensor potential. In the heavy meson sector one-pion exchange alone is strong enough to form at least deuteronlike and composites bound by approximately 50 MeV. Composites of and states bound by pion exchange alone are expected near the thresholds, while in the light meson sector one generally needs some additional short range attraction to form bound states. The quantum numbers of these states areI=0, andJ ^PC=0^–+, 1⁺⁺ for the states andI=0,J ^PC=0⁺⁺, O^–+, 1^+– and 2⁺⁺ for the composites. In the states: ^b (10545), _b1(10562) are predicted and in , one finds the states: ^b (10590), _bQ (10582),h _b(10608), _b2(10602). Near the threshold the states: ^c (3870), _c0(3870) are predicted, and near the threshold one finds the states: _b0(4015), ^c (4015),h _c(4015), _c2(4015). Within the light meson sector pion exchange gives strong attraction for and systems with quantum numbers where the best non- candidates exist, although pion exchange alone is not strong enough to support such bound states. Thus, although one cannot conclude with certainty it to be the case, this fact does favour the picture that the (1440) and thef ₁ (1420) are mainly composites and thef ₀(1710) mainly a bound state, while thef ₀(1515) andf ₂(1520) could be predominantly composites. If the predicted and states are found, these would support this interpretation of the light states. In channels with exotic flavour orCP quantum numbers pion exchange is generally repulsive or quite weak. Therefore one does not expect that such deuteronlike bound states exist, althoughB*B* may be an exception.     

Triple Regge analysis of inclusiveΛ production inK + p and π+ p interactions at 250 GeV/c

A triple Regge analysis is performedof inclusive production in the proton fragmentation region ofK ⁺+X and ⁺+X at 250 GeV/c. Slope and intercept of the leading strange meson trajectory are determined. The results obtained here are compared with those of other experiments.Partially supported by grants from CPBP 01.06 and 01.09.     

Production of neutral strange particles in muon-nucleon scattering at 490 GeV

The production ofK ⁰, and particles is studied in the E665 muon-nucleon experiment at Fermilab. The average multiplicities and squared transverse momenta are measured as a function ofx _F andW ². Most features of the data can be well described by the Lund model. Within this model, the data on the K⁰/^± ratios and on the averageK ⁰ multiplicity in the forward region favor a strangeness suppression factors/u in the fragmentation process near 0.20. Clear evidence for QCD effects is seen in the average squared transverse momentum ofK ⁰ and particles.Deceased     

O $$(\bar \Lambda /m_c )$$ effects in tests of factorization hypothesis for heavy-hadron nonleptonic decays

In the framework of the heavy-quark effective theory, theO ( O(_QCD)) corrections are estimated in the test of factorization hypothesis forB-meson nonleptonic decays proposed by Bjorken. Similar calculations are also carried out for _b nonleptonic decays. The effects of these corrections on the estimate of theD _s -meson decay constant are discussed.     

Determination of the parton distributions and structure functions of the proton from neutrino and antineutrino reactions on hydrogen and deuterium

The analytic expressions for the production cross sections of polarized bottom and top quarks ine ^* e ^– annihilation are explicitly derived at the one-loop order of strong interactions. Chirality-violating mass effects will reduce the longitudinal spin polarization for the light quark pairs by an amount of 3%, when one properly considers the massless limit for the final quarks. Numerical estimates of longitudinal spin polarization effects in the processese ^* e ^–b (g) ande ^* e ^–t (g) are presented.supported in part by the BMFT, Germany under contract 06MZ730     

Supersymmetric Box Contributions toe + e −→Z 0 h 0 ande + e −→A 0 h 0

Within the MSSM we calculate the electroweak 1-loop box contributions to the processese ⁺ e ^–Z ⁰ h ⁰ ande ⁺ e ^–Z ⁰ h ⁰. We present detailed results for c.m. energies and as well as for tan =2 and tan =50. The box contributions to the processe ⁺ e ^–Z ⁰ h ⁰ are, depending on and tan , of the order –2 to –20% and toe ⁺ e ^– A ⁰ h ⁰ of 2 to 10%.     

Measurement of the decayτ? →ρ?ντ

An analysis of the decay ^--0 v has been performed using the ARGUS detector at the DORIS II storage ring. The branching ratio has been determined to be Br(^--0 v =(22.6±0.4±0.9)%. The shape of the ^-0 invariant mass spectrum is found to be in good agreement with the predictions obtained using the conserved vector current (CVC) hypothesis, suggesting that the ^-0 system is produced in aJ ^P=1^– state. An analysis of the measured decay angular distribution of the pions with respect to the flight direction of the ^-0 system demonstrates the vector nature of the coupling at the v vertex. With the assumption of zerov mass thev spin has been shown to be .Supported by the German Bundesministerium für Forschung und Technologie, under contract number 054DO51 P     

The droplet in the tube: A case of phase transition in the canonical ensemble

We consider the 2-dimensional Ising model with ferromagnetic nearest neighbour interaction at inverse temperature. LetS _N = _t be the total magnetization inside anN×N square box, ^per be the Gibbs state in with periodic b.c., andm() be the spontaneous magnetization. We show the existence of the limit

A theoretical prediction for exclusive decaysB→K(K*)η c

The decay rates for the exclusiveB decaysBK _c andBK* _c are calculated in the context of the heavy quark effective theory. We obtain(BK _c )/ (BK)=1.6±0.2 and(BK* _c )/ (K*)=0.39±0.04. These results lead to estimates BR(BK _c )=(0.11±0.02)% and BR(BK* _c )=(0.05±0.01)% if we use the central current experimental values forB(K, K ^*) branching ratios.     

New bounds on the number of bound states for Schrödinger operators

We consider the Schrödinger operatorH = – +V(|x|) onR ³. Letn denote the number of bound states with angular momentum (not counting the 2 + 1 degeneracy). We prove the following bounds onn . LetV 0 and d/dr r ^1-2p (-V)^{1 –p} 0 for somep [1/2, 1) then

CP violation in charmlessB 0 decays: A coupled channel approach

We consider the CP-violating asymmetry betweenB ⁰f and f in the case thatf is a CP-eigenstate containing no charmed quarks. The asymmetry is assumed to arise as a result of mixing with other channelsf having the same quantum numbers but containing ac pair. Inelastic unitarity is implemented by means of the K-Matrix formalism, in which the constraints of CPT are manifestly satisfied. The formalism is applied to a hypothetical two-channel problemB ⁰M ,M , and then to a realistic four-channel situationB ^{0 + –}, ^{0 0},D ⁺ D ^–,D ^{0 0}. Asymmetries and branching ratios are estimated for the decaysB ^{0 + –}, ^{0 0}.     

Diquark Model for J/ψ Baryonic Decays

The baryonic decays of J/ provide a new way to study the internal structure of baryons. We apply a simple diquark model to the calculation of the decay cross-sections for the reactions J/ , N^*(1440), ^*N^*, and ⁰⁰. The results are different from those given by the ordinary constituent quark model. Hence these reactions may provide a new check of two different pictures for the baryons.     

A consistent parametrisation for the production rates of negatively charged hadrons and neutral strange particles in nucleon-nucleon,nucleon-nucleus and nucleus-nucleus collisions

A parametrisation of negative hadron and neutral strange particle production was developed which consistently describes presently available data from nucleon-nucleon, nucleon-nucleus and nucleus-nucleus collisions at a beam energy of 200 GeV per nucleon. Average multiplicities of negative hadrons are found to be proportional to the number of wounded nucleons, averageK _s ⁰ multiplicities proportional to the number of wounded quarks, and average and multiplicities proportional to the number of wounded quarks plus an additional contribution proportional to the number of interactions of secondary produced particles. Predictions are given for lead-lead collisions.On leave from Rudjer Boskovic Institute, Zagreb, Croatia     

Scaling and thermal equilibrium of hadrons fromZ 0 decays

An analysis of secondary hadrons fromZ ⁰ (91) decays of the LEP experiments indicates that the scaling of distributions implies the same temperatureT=0.261 GeV for all the secondaries. The multiplicities ofZ ⁰,K ⁰, ,..., and computed with their quark contents and the sameT agree with the data. The ratio of to the phase-space covered by the rapidity distribution, depends only on the energy, , fore ⁺ e ^– annihilations and collisions as well.     

ρ0 production the reaction ξξ→3π+3π?ξξ→ρ0ρ0(1700)

We have studied the ⁰ production rate in the reaction 3⁺3^– in the energy range 1.6W 7.5 GeV with the CELLO detector at PETRA. Our analysis points to a substantial yield of ^00+– events in particular atW >4.0 GeV. We give cross sections for the ⁰2⁺2^– and ^00+– final states and calculate upper limits for the reaction ⁰⁰ (1700) ^00+–.Now at CERN     

Observation of the decaya 2 − (1320)→π − η′

The reaction ^– C ^– C has been studied at 36 GeV/c. A clear signal for the decaya ₂ ^– (1320) ^– · is observed in the ^– mass spectrum. The measured ratio of branchings is BR (a ₂ ^{– –} )/BR(a ₂ ^{– –} );(3.4±0.8±0.5)·10^–2.