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D. V. Bugg

Publications and source records attributed to D. V. Bugg.

At least 37 records · Page 2Linked to original sources
arXiv2011

I = 0 C = +1 mesons from 1920 to 2410 MeV

A combined fit is presented to data on pbar-p annihilation in flight to final states eta-pizero-pizero, pizero-pizero, eta-eta, eta-etaprime and piminus-piplus. The emphasis lies in improving an earlier study of eta-pizero-pizero by fitting data at nine pbar momenta simultaneously and with parameters consistent with the two-body channels. There is evidence for all of the I=0, C=+ q-qbar states expected in this mass range. New resonances are reported with masses and widths M,Gamma as follows: JPC = 4^{-+} (2328+-38, Gamma=240+-90) MeV, 1^{++} (1971+-15, 240+-45) MeV, 0^{-+} (2285+-20, 325+-30) MeV, and 0^{-+} (2010 ^{+35}_{-60}, 270+-60) MeV. Errors on the masses and widths of other resonances are also reduced substantially. All states lie close to parallel straight line trajectories of excitation number v. mass squared.

hep-ex↗
arXiv2011

An explanation of Belle states Z_b(10610) and Z_b(10650)

Belle report data on Upsilon (5S) -> Upsilon(1S,2S,3S)-piplus-piminus and chi_b(1P,2P)-piplus-piminus; they observe peaks in Upsilon-pi and chi_b-pi consistent with J^P=1^+. They interpret the peaks as molecular states Z_b(10608) and Z_b(10653). Their masses are just above Bbar-B^* and B^*bar-B^* thresholds at 10604.6 and 10650.2 MeV. An explanation in terms of cusps at these thresholds is presented here. The product of the rising phase space for Bbar-B^* and B^*bar B^* with the cusps creates peaks a few MeV higher in Bbar-B^* and B^*bar-B^*, and these peaks can de-excite to piplus-piminus-Upsilon(1S,2S,3S) and piplus-piminus-chi_b(1P,2P).

hep-ph↗
arXiv2011

Meson Spectroscopy without Tetraquarks

Data on e+e- -> piplus-piminus-Upsilon(1S,2S,3S) show a large increase in branching fractions near Upsilon(10860). A suggestion of Ali et al. is to interpret this as evidence for a tetraquark, Yb(10890) = b-bbar. However, it may also be interpreted in terms of Upsilon(10860) -> B-B*, B*B* and BsB*s above the open-b threshold, followed by de-excitation processes such as $BB* -> Upsilon (1S,2S,3S). In the charm sector, a hypothesis open to experimental test is that X,Y and Z peaks in the mass range 3872 to 3945 MeV may all be due to regular 3P1 and 3P2 c-cbar states (and perhaps 3P0) mixed with meson-meson.

hep-ph↗
arXiv2011

An interesting feature of BESIII data for J/Psi -> gamma-(etaprime-pi-pi)

The eta(1835) is confirmed clearly in new BESIII data for J/Psi -> gamma (eta'-pi-pi); the angular distribution of the photon is consistent with a pseudoscalar. This makes it a candidate for an s-sbar radial excitation of eta' and eta(1440) (or one or both of eta(1405) and eta(1475)). However, a conspicuous feature of the BES III data is the absence of evidence for eta(1440) -> eta'-pi-pi while it is well known that eta(1440) appears in eta-pi-pi. Can these facts be reconciled? There is in fact a simple explanation. The channel eta(1440) -> eta-pi-pi may be explained by the two-step process eta(1440) -> [K*K]_{L=1} and [kappa K ]_{L=0}, followed by KK -> a0(980) -> eta-pi. This process does not produce any significant eta'-pi signal because of the Adler zero close to the eta'-pi threshold.

hep-ph↗
arXiv2010

A fresh look at eta2(1645), eta2(1870), eta2(2030) and f2(1910) in pbar-p -> eta + 3pizero

There is a large discrepancy between results of Crystal Barrel and WA102 for the branching ratio R = BR[eta2(1870)->a2(1320)pi]/ BR[eta2(1870)->f2(1270)eta]. An extensive re-analysis of the Crystal Barrel data redetermines branching ratios for decays of eta2(1870), eta2(1645), eta2(2030) and f2(1910). This re-analysis confirms a small value for R of 1.60+-0.39, inconsistent with the value 32.6+-12.6 of WA102. The likely origin of the discrepancy is that the WA102 data contain a strong f2(1910)->a2-pi signal as well as eta2(1870). There is strong evidence that the eta2(1870) has resonant phase variation. A peak in f2(1270)a0(980) confirms closely the parameters of the a2(2255) resonance observed previously. A peak in eta2(2030)-pi is interpreted naturally in terms of pi2(2245) with reduced errors for mass and width M=2285+-20(stat)+-25(syst) MeV, Gamma=250+-20(stat)+-25(syst) MeV.

hep-ex↗
arXiv2010

The covalent bond in Particle Spectroscopy

It is proposed that meson resonances are linear combinations of q-qbar and meson-meson (MM); baryon resonances are combinations of qqq and meson-baryon (MB). Mixing between these combinations arises via decays of confined states to meson-meson or meson-baryon. There is a precise analogy with the covalent bond in molecular physics; it helps to visualise what is happening physically. One eigenstate is lowered by the mixing; the other moves up and normally increases in width. Cusps arise at thresholds. At sharp thresholds due to S-wave 2-particle decays, these cusps play a conspicuous role in many sets of data.

hep-ex↗
arXiv2009

An update on the Kappa

New Focus data on Dplus -> Kminus piplus piminus are fitted to the kappa, together with earlier data from LASS, E791 and BES 2. There is a clear low mass K-pi peak due to the kappa pole. Inclusion of the I=3/2 K-pi amplitude gives only a marginal improvement to the fit and almost no change to the kappa peak. An improved formula for the kappa gives a better fit than that used earlier. The kappa pole moves to 663 +- 8(stat) +- 34(syst) -i[329 +- 5(stat) +- 22(syst)] MeV. The K0(1430) pole is at 1427 +- 4(stat) +- 13(stat) -i[135 +- 5(stat) +- 20(syst)] MeV.

hep-ph↗
arXiv2009

Parity doubling of highly excited mesons

Glozman has proposed that highly excited mesons and baryons fall into parity doublets, and that the f4(2050) on the leading Regge trajectory should have a nearly degenerate J^{PC} = 4^{-+} partner. A re-analysis of Crystal Barrel data does not support this idea. A likely explanation is that centrifugal barriers on the leading trajectory allow formation of the L=J-1 states, but are too strong to allow L=J states. Two new polarisation experiments have the potential for major progress in meson spectroscopy.

hep-ex↗
arXiv2009

Data on J/Psi -> gamma(Kcharged-Kshort-picharged) and gamma(eta-piplus-piminus)

Data on J/Psi -> gamma (eta-piplus-piminus) and gamma (Kcharged-Kshort-picharged) from 58M J/Psi hadronic interactions in the BES II detector are analysed. They throw new light on J^P = 0^- mesons throughout the mass range up to 2 GeV, notably eta(1440). For the first time, this state is fitted including the full s-dependence of decays to a0(980)-pi, eta-sigma, Kstar-K, kappa-K and f0(980)-eta, including the dispersive term associated with this s-dependence. Two types of fit are reported. The first uses a single eta(1440). The second uses separate eta(1405) and eta(1475). The strong s-dependence of P-wave production of Kstar-K shifts the fitted mass of eta(1475) down to 1440 MeV. As a result, the two types of fit give almost identical results and the conclusion from these data is that there is no significant evidence for two separate resonances. In KKpi, there are definite though small contributions from f1(1420) and f1(1285). The optimum fit requires either a small additional f1(1510) or alternatively a small perturbation to the high mass tail of f1(1420). At higher masses, there is a broad J^P=0^- peak in eta-pi-pi at 1850 MeV. There is also a weak but definite signal consistent with eta2 (1870) -> eta-pi-pi.

hep-ex↗
arXiv2009

Study of J/Psi -> gamma (piplus-piminus-piplus-piminus)

BES II data for the channel J/Psi -> gamma (piplus-piminus-piplus-piminus) are analysed from a sample of 58M J/Psi hadronic interactions. They reveal further detail in the J^{PC} = 0^{-+} sector for the 4pi channel. A broad 0^{-+} -> rho-rho component extending from 1500 to 2400 MeV is fitted. A narrower structure reveals a new J^P = 0^- contribution requiring a resonance of mass 1970 +- 25(stat) +- 60(syst) MeV and width Gamma = 210 +- 25(stat) +- 60(syst) MeV. There is also tentative evidence for a 0^- resonance with mass 1560 +- (25) +- 60(syst) MeV and width ~280 MeV. In the 0^{+} sector, there are clear contributions from f0(1500) and f0(1790). The observed f0(1790) is visibly distinct from f0(1710) and confirms the existence of f0(1790); its mass 1800 +- 25(stat) +- 20(syst) MeV and width 230 +- 30(stat) +- 25(syst) MeV are better determined here than elsewhere.

hep-ex↗
arXiv2009

The D-pi S-wave

A pole in the D-pi S-wave analogous to the sigma and kappa is predicted at 2098 +- 40 - i(260 +- 40) MeV. The main objective of this paper is to provide formulae for fitting it to data.

hep-ph↗
arXiv2009

An alternative fit to Belle mass spectra for DD, D*D* and Lambda_C Lambda_c

Peaks observed by Belle in DD at 3.878 GeV and in D*D* at 4.156 GeV may be fitted by phase space multiplied by a form factor with an RMS radius of interaction 0.63 fm. The peak observed in Lambda_C Lambda_C at 4.63 GeV may be explained by Y(4660), multiplied by a corresponding form factor with RMS radius 0.94 fm.

hep-ph↗
arXiv2008

Re-analysis of data on a0(1450) and a0(980)

Four sets of data determining parameters of a0(1450) and a0(980) are re-analysed. These are Crystal Barrel data for pbar-p annihilation at rest to eta-pizero-pizero in (i) liquid hydrogen and (ii) gas, and to (iii) K0_L-picharged-Kcharged and (iv) omega piplus-piminus-pizero (mostly omega-rho-pi). Dispersive corrections due to opening of inelastic thresholds are treated fully. This stabilises parameters of a0(1450) substantially. The mass of its peak is 1448 +-13(stat) +- 25(syst) MeV and its mean full width at half maximum is 192 +-9 +-9 MeV. The pole position is 1432 +- 13 +- 25 - i(98 +-5 +-5) MeV. At the peak, eta-pi, omega-rho and a0(980)-sigma decay intensities are in the ratios 1 : 9.2 +- 0.8 +- 1.3 : 3.1 +- 0.2 +- 0.9. There is no evidence for a separate a0 near 1300 MeV claimed by Obelix. Parameters of a0(980) are updated to M = 987.4 +- 1.0 +- 3.0 MeV, g^2(eta-pi) = 0.164 +- 0.007 +- 0.010 GeV^2, g^2(KK)/g^2(eta-pi) = 1.05 +- 0.07 +- 0.05. The nature of the prominent J^{PC} = 0^{-+} signal in omega-rho is also clarified.

hep-ex↗
arXiv2008

Synchonisation of Resonances with Thresholds

The mechanism by which a resonance may be attracted to a sharp threshold is described with several examples. It involves a threshold cusp interfering constructively with either or both (i) a resonance produced via confinement, (ii) attractive t- and u-channel exchanges. More generally, it is suggested that resonances are eigenstates generated by mixing between confined states and long-range meson and baryon exchanges.

hep-ph↗
arXiv2008

Review of Scalar Mesons

The formulae needed to parametrise sigma, kappa, a0(980) and f0(980) are reviewed. For sigma and kappa, the Adler zero due to Chiral Symmetry Breaking plays a crucial role. The f0(980) and a0(980) are locked to the KK threshold by a cusp mechanism which leads to a sharp peak in attraction at the threshold. This mechanism may play a wider role. A novel suggestion is that the confinement potential involves a cooperative effect between QCD effects (coloured quarks and gluons) and conventional meson exchanges.

hep-ph↗
arXiv2008

Experiments needed in Meson and Baryon Spectroscopy

Three (or four) straightforward experiments would contribute greatly to completing the spectroscopy of baryons and light mesons. In the baryon sector, data are needed on inelastic reactions from a polarised target with pi and kaon beams up to 3 GeV/c. Similar data are needed in the light meson sector for pbar-p interactions in the momentum range 0.3 to 2 GeV/c. In both cases, valuable information is to be obtained from longitudinal (L) and sideways (S) target polarisations as well as the conventional normal (N) polarisation. Thirdly, 3S_1 and 3D_1 mesons in the mass range 1 to 2.4 GeV/c could probably be separated either by diffractive dissociation of transversely polarised photons or by radiative return experiments using transversely and longitudinally polarised electrons.

hep-ex↗
arXiv2008

How Resonances can synchronise with Thresholds

The mechanism by which a threshold may capture a resonance is examined. It involves a threshold cusp interfering constructively with either or both (i) a resonance produced via confinement, (ii) attractive t- and u-channel exchanges. The fo(980), X(3872) and Z(4430) are studied in detail. The fo(980) provides a valuable model of the locking mechanism. The X(3872) is too narrow to be fitted by a cusp, and requires either a resonance or virtual state. The Z(4430) can be fitted as a resonance but also can be fitted successfully by a cusp with no nearby resonant pole.

hep-ph↗