86,994 research outputs found
Il gioco Euristico con gli oggetti
No full textMOVIMENTO, (RIVISTA DI PSICOLOGIA E SCIENZE DEL MOVIMENTO), N.1 . , GENN-APR.2005, ISSN:0393-9340, EDIT.LUIGI POZZI, ROMA
Absorption in Heavy Ion Collisions
No full textWe present a new calculation of the pi-J/psi dissociation cross sections within the Constituent Quark-Meson Model recently introduced. To discuss the absorption of J/psi in heavy-ion collisions, we assume the J/psi to be produced inside a thermalized pion gas, as discussed by Bjorken, and introduce the corrections due to absorption by nuclear matter as well. We fit the absorption length of the J/psi to the data obtained at the CERN SPS by the NA50 Collaboration for Pb-Pb collisions. Collisions of lower centrality allow us to determine the temperature and the energy density of the pion gas. For both these quantities we find values close to those indicated by lattice gauge calculations for the transition to a quark-gluon plasma. A simple extrapolation to more central collisions, which takes into account the increase of the energy deposited due to the increased nucleon flux, fails to reproduce the break in J/psi absorption indicated by NA50, thus lending support to the idea that an unconfined quark-gluon phase may have been produced. This conclusion could be sharpened by analysing in a similar way, as a function of centrality, other observables such as strange particle production.We present a new calculation of the pi-J/psi dissociation cross sections within the Constituent Quark-Meson Model recently introduced. To discuss the absorption of J/psi in heavy-ion collisions, we assume the J/psi to be produced inside a thermalized pion gas, as discussed by Bjorken, and introduce the corrections due to absorption by nuclear matter as well. We fit the absorption length of the J/psi to the data obtained at the CERN SPS by the NA50 Collaboration for Pb-Pb collisions. Collisions of lower centrality allow us to determine the temperature and the energy density of the pion gas. For both these quantities we find values close to those indicated by lattice gauge calculations for the transition to a quark-gluon plasma. A simple extrapolation to more central collisions, which takes into account the increase of the energy deposited due to the increased nucleon flux, fails to reproduce the break in J/psi absorption indicated by NA50, thus lending support to the idea that an unconfined quark-gluon phase may have been produced. This conclusion could be sharpened by analysing in a similar way, as a function of centrality, other observables such as strange particle production.We present a new calculation of the pi-J/psi dissociation cross sections within the Constituent Quark-Meson Model recently introduced. To discuss the absorption of J/psi in heavy-ion collisions, we assume the J/psi to be produced inside a thermalized pion gas, as discussed by Bjorken, and introduce the corrections due to absorption by nuclear matter as well. We fit the absorption length of the J/psi to the data obtained at the CERN SPS by the NA50 Collaboration for Pb-Pb collisions. Collisions of lower centrality allow us to determine the temperature and the energy density of the pion gas. For both these quantities we find values close to those indicated by lattice gauge calculations for the transition to a quark-gluon plasma. A simple extrapolation to more central collisions, which takes into account the increase of the energy deposited due to the increased nucleon flux, fails to reproduce the break in J/psi absorption indicated by NA50, thus lending support to the idea that an unconfined quark-gluon phase may have been produced. This conclusion could be sharpened by analysing in a similar way, as a function of centrality, other observables such as strange particle production.We present a new calculation of the π – J / ψ dissociation cross sections within the constituent quark–meson model recently introduced. To discuss the absorption of J / ψ in heavy-ion collisions, we assume the J / ψ to be produced inside a thermalized pion gas, as discussed by Bjorken, and introduce the corrections due to absorption by nuclear matter as well. We fit the absorption length of the J / ψ to the data obtained at the CERN SPS by the NA50 Collaboration for Pb–Pb collisions. Collisions of lower centrality allow us to determine the temperature and the energy density of the pion gas. For both these quantities we find values close to those indicated by lattice gauge calculations for the transition to a quark–gluon plasma. A simple extrapolation to more central collisions, which takes into account the increase of the energy deposited due to the increased nucleon flux, fails to reproduce the break in J / ψ absorption indicated by NA50, thus lending support to the idea that an unconfined quark–gluon phase may have been produced. This conclusion could be sharpened by analysing in a similar way, as a function of centrality, other observables such as strange particle production
The new resonances Zcs(3985) and Zcs(4003) (almost) fill two tetraquark nonets of broken SU(3)f
No full textNew data from BESIII and LHCb indicate the existence of two hidden charm, open strangeness resonances, Zcs(3985) and Zcs(4003). The near degeneracy of Zcs(3985) and Zcs(4003) reproduces, in the strange sector, the situation observed with X(3872) and Zc(3900). We show that, in the tetraquark picture, the Zcs resonances neatly fit into two SU(3)f nonets with JP = 1+ and oppo- site charge-conjugation, together with X(3872), X(4140) and Zc(3900). The mass of the missing element of the nonets is predicted. The classification represents a significative score in favour of the tetraquark model
Apaf1 in embryonic development-shaping life by death, and more
No full textApaf1 has been studied hitherto for its key role in regulating the formation of the apoptotic core machinery, the apoptosome, to induce programmed cell death. Apaf1 involvement in orchestrating this process during embryonic development has been widely documented and constitutes a breakthrough in developmental biology. In this review, we aim to highlight the origin of Apaf1 discoveries and how findings, mainly based on the analysis of knock-out mouse models, have led us to consider Apaf1 as a master player in fine-tuning apoptosis during embryonic development. Likewise, we also attempt to establish how Apaf1 function is locally time-dependent in regulating neurodevelopment and becomes dispensable during neuron maturation. We go on to discuss Apaf1's new functions which have been unveiled in recent years and which could revise or, at least, adjust the common view of Apaf1 having merely an apoptotic role. Hence, by presenting clear indications on the pro-survival roles of Apaf1, this review seeks to provide novel and more complex insights into Apaf1 involvement in nervous system development
Four-Quark Mesons
No full textThe features of a model interpreting the light scalar mesons as diquark-antidiquark bound states and the consequences of its natural extension to include heavy quarks are briefly reviewed.The features of a model interpreting the light scalar mesons as diquark-antidiquark bound states and the consequences of its natural extension to include heavy quarks are briefly reviewed.The features of a model interpreting the light scalar mesons as diquark‐antidiquark bound states and the consequences of its natural extension to include heavy quarks are briefly reviewed
Lepton asymmetry in B decays in the superweak and in the standard theory of CP violation
No full textThe predictions of the superweak theory of CP violation for semileptonic neutral B meson decays are considered. The charge asymmetry in conjunction with the measurements of fB is seen to be a promising way to distinguish the superweak from the standard theory
A new look at scalar mesons
No full textLight scalar mesons are found to fit rather well a diquark-antidiquark description. The resulting nonet obeys mass formulae which respect, to a good extent, the OZI rule. OZI allowed strong decays are reasonably reproduced by a single amplitude describing the switch of a qbar-q pair, which transforms the state into two colourless pseudoscalar mesons. Predicted heavy states with one or more quarks replaced by charm or beauty are briefly described; they should give rise to narrow states with exotic quantum numbers.Light scalar mesons are found to fit rather well a diquark-antidiquark description. The resulting nonet obeys mass formulae which respect, to a good extent, the OZI rule. OZI allowed strong decays are reasonably reproduced by a single amplitude describing the switch of a qbar-q pair, which transforms the state into two colourless pseudoscalar mesons. Predicted heavy states with one or more quarks replaced by charm or beauty are briefly described/ they should give rise to narrow states with exotic quantum numbers
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