IV Encontro Nacional de Física Hadrónica

Universidade de Coimbra

12 Janeiro 2005

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Alberto, Pedro Vieira DFUC

Bicudo, Pedro CFIF, Dep. Física, IST The pentaquark in the linear molecular heptaquark model
The status of the pentaquarks Theta5, Xi*5 and D-p5 is first reviewed. Then multiquarks are studied microscopically in a standard quark model. In pure ground-state pentaquarks the short-range interaction is computed and it is shown to be repulsive. Such a system would have a very broad decay width, different from the observed pentaquarks. An excitation is needed for stability, and an additional quark-antiquark pair is then considered. The quarks assemble in three hadronic clusters, and the central hadron provides stability. This is suggested to produce a quite stable linear molecular system. The possible crypto-heptaquark hadrons with exotic pentaquark flavours, with any number of strange, charmed and bottomed quarks, are listed. The importance of medium-range interactions and of the coupling to two-body decay channels is also discussed.

Bordalo, Paula LIP

Borges, Gonçalo LIP(Lisboa Summary on NA38/NA50 J/psi normal nuclear absorption
We will present some final results regarding the normal J/psi nuclear absorption, using J/psi absolute cross-section measurements and J/psi/DY cross-section ratios, obtained in proton-nucleus induced interactions in NA50 and NA38 experiments at CERN/SPS. Such measurements are very important to correctly understand the "anomolous" suppression of J/psi production, predicted as an unambigous signature of Quark Gluon Plasma formation and experimentally observed by NA50 experiment in heavy-ion collisions.

Carvalho, João LIP, Dep. Física, U. Coimbra

Castro, Nuno LIP

Coimbra, Rita Alexandra CFC, Dep. Física, U. Coimbra Classical Solutions of SU(3) Yang-Mills Theory and Heavy Quarkonia

Costa, Pedro CFT, Dep. Física, U. Coimbra The restoration of the U_A(1) symmetry and the pseudoscalar meson spectrum in hot, dense matter

Hiller, Brigitte U. Coimbra The 't Hooft determinant resolution of the eta' puzzle
A.A. Osipov, A.H. Blin, B. Hiller, hep-ph/0410148
The six-quark instanton induced 't Hooft interaction, which breaks the U_A(1) symmetry of QCD, is also a source of semi-classical corrections to the low energy effective action. We argue that there emerges a dimensionless expansion parameter that introduces a new mass scale L~2.4 GeV, in the 0^-,0^+ channels. This scale plays a similar role as the large critical mass discovered in the framework of QCD sum rules in the 0^-,0^+ gluonic channels. In particular, it allows to resolve the eta' puzzle.

Kleefeld, Frieder CFIF, IST Is QCD THE Theory of Strong (i.e. Hadronic) Interactions?
Great parts of the scientific community believe - not only after the award of the Nobel-Prize 2004 - that Quantum Chromodynamics (QCD) is the theory of strong interactions. We want to report on recent scientific results which clearly proof that there exist - against the common sense - "naively forbidden" alternatives to QCD which should be considered seriously.

Moskal, Pawel Jagellonian University, Poland Experimental study of the nucleon-meson and nucleon-hyperon interactions at COSY-11

Oliveira, Orlando CFC, Dep. Física, U. Coimbra

Onofre, António LIP Study of ATLAS sensitivity to Forward-Backward Asymmetries in top decays
The ATLAS experimental sensitivity to Forward-Backward assymetries was studied using simulated tt events generated for the LHC. The dominant Standard Model decay of the top quark, t->bW, was assumed. One of the W is expected to decay hadronically and the other through the leptonic channel. Results are presented for the angular distribution between the lepton from the W decay and the b-quark associated to the same parent t-quark, measured in the W centre-of-mass system.

Quintans, Catarina LIP Recent results from the COMPASS experiment

Ramos, Sergio Lip - Lisboa Pentaquark search in the COMPASS experiment

Lip - Lisboa Pentaquark search in the COMPASS experiment

Rupp, George CFIF, IST Unravelling the curious SELEX state D_s(2632)
Eef van Beveren, George Rupp
We study bound states below threshold and resonances above threshold in the D0-K+ and Ds-eta systems, using a many-coupled-channel model for non-exotic meson-meson scattering applied to states with the quantum numbers of c-sbar quark-antiquark vector mesons. We fit the ground state at 2.112 GeV, whence the lowest resonances in D0-K+ come out at 2.61, 2.72, 3.03, and 3.08 GeV. The resonance at 2.61 GeV acquires a width of about 8 MeV, while its partial P-wave cross section is up to six times larger in Ds-eta than in D0-K+, provided a mechanism accounting for Okubo-Zweig-Iizuka-forbidden decays is included. The latter finding is in agreement with the observations of the SELEX collaboration with respect to the recently reported DsJ(2632) resonance. Therefore, we conclude that the DsJ(2632) is most probably the first recurrence of the Ds*(2112) meson. Published in Phys. Rev. Lett. 93 (2004) 202001 [hep-ph/0407281].

Santos, Helena LIP Final results on charmonia production at the NA50 experiment
The final results on charmonia production in Pb-Pb interactions at 158~GeV/c per nucleon incident momentum, obtained from data collected by the NA50 experiment at the CERN-SPS, are discussed in detail. A strong $J/\psi$ suppression as a function of the collisions centrality is observed. We also report the recent development on the normal nuclear absorption extraction, now based on proton--induced reactions only. A comparison made with Pb-Pb results suggests the onset of an anomalous $J/\psi$ suppression mechanism. This feature contrasts with the suppression observed in the lighter O--Cu, O--U and S--U collisions systems, which follow the extrapolated p--A behaviour. Regarding the $\psi'$ production in heavy ion interactions, also a strong suppression of this vector--meson as a function of the collisions centrality sets in, already in S-U reactions. Its production rate decreases with increasing centrality and is significantly lower than the rate measured in proton-induced collisions.

Silva, Luis LIP

Silva, Paulo CFC, Dep. Física, U. Coimbra The IR gluon propagator from Lattice QCD

Veloso, Filipe LIP The ATLAS experiment sensitivity to Flavour Changing Neutral Currents top decays (t->qZ, t->q\gamma and t->qg) was studied. Different analyses, corresponding to the tt production and single top production at LHC, with subsequent anomalous top decays t->qX (X=Z,\gamma,g), are presented. The branching ratio sensitivity (assuming a 5 sigma signal significance) and 95% confidence level limits on the branching ratio (in the absence of signal hypothesis) were obtained.

Villate, Jaime E. Fac. Eng. Univ. Porto

Last update: 23 November 2004

Alberto, Pedro Vieira	DFUC
Bicudo, Pedro	CFIF, Dep. Física, IST	The pentaquark in the linear molecular heptaquark model The status of the pentaquarks Theta5, Xi*5 and D-p5 is first reviewed. Then multiquarks are studied microscopically in a standard quark model. In pure ground-state pentaquarks the short-range interaction is computed and it is shown to be repulsive. Such a system would have a very broad decay width, different from the observed pentaquarks. An excitation is needed for stability, and an additional quark-antiquark pair is then considered. The quarks assemble in three hadronic clusters, and the central hadron provides stability. This is suggested to produce a quite stable linear molecular system. The possible crypto-heptaquark hadrons with exotic pentaquark flavours, with any number of strange, charmed and bottomed quarks, are listed. The importance of medium-range interactions and of the coupling to two-body decay channels is also discussed.
Bordalo, Paula	LIP
Borges, Gonçalo	LIP(Lisboa	Summary on NA38/NA50 J/psi normal nuclear absorption We will present some final results regarding the normal J/psi nuclear absorption, using J/psi absolute cross-section measurements and J/psi/DY cross-section ratios, obtained in proton-nucleus induced interactions in NA50 and NA38 experiments at CERN/SPS. Such measurements are very important to correctly understand the "anomolous" suppression of J/psi production, predicted as an unambigous signature of Quark Gluon Plasma formation and experimentally observed by NA50 experiment in heavy-ion collisions.
Carvalho, João	LIP, Dep. Física, U. Coimbra
Castro, Nuno	LIP
Coimbra, Rita Alexandra	CFC, Dep. Física, U. Coimbra	Classical Solutions of SU(3) Yang-Mills Theory and Heavy Quarkonia
Costa, Pedro	CFT, Dep. Física, U. Coimbra	The restoration of the U_A(1) symmetry and the pseudoscalar meson spectrum in hot, dense matter
Hiller, Brigitte	U. Coimbra	The 't Hooft determinant resolution of the eta' puzzle A.A. Osipov, A.H. Blin, B. Hiller, hep-ph/0410148 The six-quark instanton induced 't Hooft interaction, which breaks the U_A(1) symmetry of QCD, is also a source of semi-classical corrections to the low energy effective action. We argue that there emerges a dimensionless expansion parameter that introduces a new mass scale L~2.4 GeV, in the 0^-,0^+ channels. This scale plays a similar role as the large critical mass discovered in the framework of QCD sum rules in the 0^-,0^+ gluonic channels. In particular, it allows to resolve the eta' puzzle.
Kleefeld, Frieder	CFIF, IST	Is QCD THE Theory of Strong (i.e. Hadronic) Interactions? Great parts of the scientific community believe - not only after the award of the Nobel-Prize 2004 - that Quantum Chromodynamics (QCD) is the theory of strong interactions. We want to report on recent scientific results which clearly proof that there exist - against the common sense - "naively forbidden" alternatives to QCD which should be considered seriously.
Moskal, Pawel	Jagellonian University, Poland	Experimental study of the nucleon-meson and nucleon-hyperon interactions at COSY-11
Oliveira, Orlando	CFC, Dep. Física, U. Coimbra
Onofre, António	LIP	Study of ATLAS sensitivity to Forward-Backward Asymmetries in top decays The ATLAS experimental sensitivity to Forward-Backward assymetries was studied using simulated tt events generated for the LHC. The dominant Standard Model decay of the top quark, t->bW, was assumed. One of the W is expected to decay hadronically and the other through the leptonic channel. Results are presented for the angular distribution between the lepton from the W decay and the b-quark associated to the same parent t-quark, measured in the W centre-of-mass system.
Quintans, Catarina	LIP	Recent results from the COMPASS experiment
Ramos, Sergio	Lip - Lisboa	Pentaquark search in the COMPASS experiment
Lip - Lisboa	Pentaquark search in the COMPASS experiment
Rupp, George	CFIF, IST	Unravelling the curious SELEX state D_s(2632) Eef van Beveren, George Rupp We study bound states below threshold and resonances above threshold in the D0-K+ and Ds-eta systems, using a many-coupled-channel model for non-exotic meson-meson scattering applied to states with the quantum numbers of c-sbar quark-antiquark vector mesons. We fit the ground state at 2.112 GeV, whence the lowest resonances in D0-K+ come out at 2.61, 2.72, 3.03, and 3.08 GeV. The resonance at 2.61 GeV acquires a width of about 8 MeV, while its partial P-wave cross section is up to six times larger in Ds-eta than in D0-K+, provided a mechanism accounting for Okubo-Zweig-Iizuka-forbidden decays is included. The latter finding is in agreement with the observations of the SELEX collaboration with respect to the recently reported DsJ(2632) resonance. Therefore, we conclude that the DsJ(2632) is most probably the first recurrence of the Ds*(2112) meson. Published in Phys. Rev. Lett. 93 (2004) 202001 [hep-ph/0407281].
Santos, Helena	LIP	Final results on charmonia production at the NA50 experiment The final results on charmonia production in Pb-Pb interactions at 158~GeV/c per nucleon incident momentum, obtained from data collected by the NA50 experiment at the CERN-SPS, are discussed in detail. A strong $J/\psi$ suppression as a function of the collisions centrality is observed. We also report the recent development on the normal nuclear absorption extraction, now based on proton--induced reactions only. A comparison made with Pb-Pb results suggests the onset of an anomalous $J/\psi$ suppression mechanism. This feature contrasts with the suppression observed in the lighter O--Cu, O--U and S--U collisions systems, which follow the extrapolated p--A behaviour. Regarding the $\psi'$ production in heavy ion interactions, also a strong suppression of this vector--meson as a function of the collisions centrality sets in, already in S-U reactions. Its production rate decreases with increasing centrality and is significantly lower than the rate measured in proton-induced collisions.
Silva, Luis	LIP
Silva, Paulo	CFC, Dep. Física, U. Coimbra	The IR gluon propagator from Lattice QCD
Veloso, Filipe	LIP	The ATLAS experiment sensitivity to Flavour Changing Neutral Currents top decays (t->qZ, t->q\gamma and t->qg) was studied. Different analyses, corresponding to the tt production and single top production at LHC, with subsequent anomalous top decays t->qX (X=Z,\gamma,g), are presented. The branching ratio sensitivity (assuming a 5 sigma signal significance) and 95% confidence level limits on the branching ratio (in the absence of signal hypothesis) were obtained.
Villate, Jaime E.	Fac. Eng. Univ. Porto