arXiv subjects

Frank Close

Publications and source records attributed to Frank Close.

17 recordsLinked to original sources

arXiv2010

Novel Charmonium and Bottomonium Spectroscopies due to Deeply Bound Hadronic Molecules from Single Pion Exchange

Pion exchange in S-wave between hadrons that are themselves in a relative S-wave is shown to shift energies by hundreds of MeV, leading to deeply bound quasi-molecular states. In the case of charmed mesons $D^*,D_1$ a spectroscopy arises consistent with enigmatic charmonium states observed above 4 GeV in $e^+e^-$ annihilation. A possible explanation of $Y(4260)\to \psi\pi\pi$ and $Y(4360) \to \psi'\pi\pi$ is found. We give results for all isospin and charge-conjugation combinations, and comment on flavor exotic doubly charmed states and bottomonium analogs. A search in $D\bar{D}3\pi$ is recommended to test this hypothesis. An exotic $1^{-+}$ is predicted to occur in the vicinity of the $Y$(4260).

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arXiv2009

On the possibility of Deeply Bound Hadronic Molecules from single Pion Exchange

Pion exchange in S-wave between hadrons that are themselves in a relative S-wave can shift energies by hundreds of MeV. In the case of charmed mesons $D,D^*,D_0,D_1$ a spectroscopy of quasi-molecular states may arise consistent with enigmatic charmonium states observed above 4 GeV in $e^+e^-$ annihilation. A possible explanation of $Y(4260)\to ψππ$ and $Y(4360) \to ψ'ππ$ is found. Searches in $D\bar{D}3π$ channels as well as B decays are recommended to test this hypothesis.

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arXiv2008

Charmonium production in e+e- to ψ+ X(c\bar c) and e+e- to D*D_J

The dominance of chi_0 in the data for e+e- to psi + chi_J(c\bar{c}) is shown to violate OZI factorization. Single gluon exchange gives a non-factorizing effective S.L interaction that generates a large scalar production amplitude. This also has observable effects near threshold in e+e- to D*D_J, where enhancements of D*D_0 and DD_1 channels are predicted. Further tests and implications are discussed.

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arXiv2008

Three flavours of Hybrid or $π$ exhange: which is more attractive?

This review summarises issues that have arisen since the appearance of "Rumsfeld Hadrons". We show that signals $ϕ(2175)$; Y(4260) and $Υ(10890)$ in the \ssbar, \cc and \bb share features that point to the possible role of $π$ exchange forces between flavoured mesons generating effects that can mimic hybrid mesons. The flavour dependence of these phenomena may help to resolve this question.

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arXiv2003

The End of the Constituent Quark Model?

In this conference summary talk at Hadron03, questions and challenges for Hadron physics of light flavours are outlined. Precision data and recent discoveries are at last exposing the limitations of the naive constituent quark model and also giving hints as to its extension into a more mature description of hadrons. These notes also pay special attention to the positive strangeness baryon $Θ^+(1540)$ and include a pedagogic discussion of wavefunctions in the pentaquark picture, their relation with the Skyrme model and related issues of phenomenology.

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arXiv1997

Two Photon Physics at LEP2

The working group on two photon physics concentrated on three main subtopics: modelling the hadronic final state of deep inelastic scattering on a photon; unfolding the deep inelastic scattering data to obtain the photon structure function; and resonant production of exclusive final states, particularly of glueball candidates. In all three areas, new results were presented.

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arXiv1997

Scalar Glueball and Friends

The $f_0(1500)$ is identified in three glueball favoured production mechanisms: $p\bar{p}$ annihilation, $ψ\to γf_0$ and Central Production. The production rate for glueballs in $ψ\to γG$ has been quantified and the $f_0(1500)$ is found to be consistent with a glueball - $q\bar{q}$ mixture. We illustrate a remarkable property of central production where kinematic cuts appear to make a systematic separation between glueballs and $q\bar{q}$ of the same $J^{PC}$. When the cut favouring glueballs is applied, the $f_0(1500)$ and other enigmatic states appear prominently while confirmed $q\bar{q}$ states are empirically suppressed.

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arXiv1997

A Glueball- $q\bar{q}$ Filter in Central Hadron Production

We have stumbled upon a remarkable empirical feature of central meson production which separates established $q\bar{q}$ mesons from glueball candidates. This does not appear to have been noted previously and we have no simple explanation for it. We suggest that glueballs and $q\bar{q}$ of the same $J^{PC}$ are distinguishable due to their boson versus fermion internal structure and that this leads to a different topology for central production of glueballs and $q\bar{q}$. Upon application of this test to data from the WA102 experiment we find that the $f_0(1500)$ and the $f_{2}(1900)$ show behaviour consistent with glueballs and opposite to that exhibited by established $q\bar{q}$ states.

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arXiv1996

The current picture of Glueballs

Some recent developments in the phenomenology of the lightest scalar glueball are summarised. Tools for determining the gluonic content of a resonance of known mass, width and $J^{PC}$ from its branching fraction in radiative quarkonium decays and production cross section in $γγ$ collisions are presented. Two $q\bar{q} - G$ mixing schemes for $J^{PC} = 0^{++}$, inspired by the lattice, are shown to lead to similar phenomenology that may be tested at BEPC and in $γγ$ production at LEP2.

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arXiv1996

Final State Interactions, Resonances and CP Violation in D and B Exclusive Decays

Hadron resonances affect nonexotic $D^o$ decays but not $B$ decays which are far from the resonance region. We obtain new information from {\bf exclusive} decays and show that interference between colour favoured and colour suppressed diagrams is {\bf constructive} in $B$ and (some) $D$ decays in contrast to the inclusive decays where a net Pauli destructive interference is claimed. We suggest that a systematic study of $B$ decay final states containing excited mesons such as $a_1 D$ or $πD^{**}$ show opposite behaviour for $B^o$ and $B^+$ relative to the ground state channels. We give inequalities among final state branching ratios for several $B$ and $D$ channels. Decays into $πK^{(*)}$ and $ρK^{(*)}$ appear to show different behaviours.

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arXiv1995

Nucleon Spin: Summary

This talk summarises the discussions during the conference on the spin structure of the nucleon held at Erice; July 1995. The summary focuses on where we have come, where we are now, and the emerging questions that direct where we go next in the quest to understand the nucleon spin.

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arXiv1995

Are Glueballs and Hybrids Found?

The lightest scalar glueball and ground state hybrids may have been found. I compare signals reported at this conference with theoretical expectations and highlight the questions that need to be addressed in forthcoming experiments.

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arXiv1995

Is $f_0(1500)$ a Scalar Glueball?

Following the discovery of two new scalar mesons, $f_0(1370)$ and $f_0(1500)$ at the Low Energy Antiproton Ring at CERN, we argue that the observed properties of this pair are incompatible with them both being $\qqbar$ mesons. We show instead that $f_0(1500)$ is compatible with the ground state glueball expected around 1500 MeV mixed with the nearby states of the $0^{++}$ $Q\bar{Q}$ nonet. Tests of this hypothesis include the prediction of a further scalar state, $f_0'(1500 - 1800)$ which couples strongly to $K\bar{K}$, $ηη$ and $ηη'$. Signatures for a possible tensor glueball at $\sim $2 GeV are also considered.

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arXiv1995

EVIDENCE FOR A SCALAR GLUEBALL

We show that the newly discovered scalar meson $f_0(1500)$ at LEAR has properties compatible with the lightest scalar glueball predicted by lattice QCD and incompatible with a $\qqbar$ state. We suggest that decays of glueballs are into pairs of glueballs (including $η, η'$ or $(ππ)_S$) or by mixing with nearby $Q\bar{Q}$ states. The partial widths of $f_0(1500)$ are in accord with this hypothesis, tests of which include characteristic radiative decays to $γϕ,γω, γρ$ and the prediction of a further scalar state, $f_0'(1500 - 1800)$ which couples strongly to $K\bar{K}$, $ηη$ and $ηη'$.

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arXiv1994

New Metastable Charmonium and the $ψ'$ Anomaly at CDF

Production of metastable charmonium states more massive than the $ψ(3685)$ is expected in models and could be the source of up to $50\%$ of the $ψ$ observed at large $p_T$ at the Tevatron.Narrow $2^{-+},2^{--} c\bar{c}$ are predicted at around 3.8GeV and radially excited $2^3P_{1,2}$ may also have suppressed hadronic widths making these states potentially extra sources of $ψ(3685)$. Colour octet components are believed to dominate $ψ$ production at the Tevatron which suggests that hybrid charmonium production may also be prominent. Estimates of hybrid production rates and branching ratios into charmonium suggest that metastable hybrids with mass $\approx$ 4GeV may play an important role in generating the observed $ψ(3685),ψ(3095)$

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arXiv1993

Hadrons and Glue at a Tau-Charm Factory

I discuss the special opportunities that a Tau-Charm Factory offers for identifying gluonic excitations, hybrid charmonium and other exotic hadronic states. (Invited talk at TCF Workshop, Marbella, 1-6June)

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arXiv1992

Effective Heavy Quark Theory

We show how heavy quark effective theory, including 1/M corrections, may be matched onto dynamical quark models by making a specific choice of K,m and v in the p=mv+K expansion. We note that Wigner rotations of heavy quark spins arise at $O(p^2/m^2)$ in non-relativistic models but at $O(\Lambda_{QCD}/M_Q)$ or O(velocity-transfer) in HQET and so are necessary for a consistent treatment.

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