scholarly journals XYZ states as hadronic molecules

2019 ◽  
Vol 202 ◽  
pp. 01002
Author(s):  
A.V. Nefediev

In the past decade, a lot of new hadrons containing heavy quarks were discovered which do not fit into the scheme provided by the traditional quark models. Such states are known as the XYZ states and they are conventionally referred to as exotic ones. At present, there is no consensus on their nature, and different models and approaches have been suggested to explain their unusual properties. The talk is devoted to a brief overview of the molecule model for such exotic states.

2019 ◽  
Vol 212 ◽  
pp. 02006
Author(s):  
Jens Sören Lange

Recent results of exotic states with heavy quarks, denoted as XYZ states, are presented. The results include searches for the Y(4260) in B meson decays, a spin partner of Y(4630), and the strange Pentaquark $ P_s^ + $. An addition, the measurements of the absolute branching fraction of X(3872) and search for double Zc production is dicussed.


2014 ◽  
Vol 35 ◽  
pp. 1460411
Author(s):  
STUART FEGAN

The 12 GeV upgrade to the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab will enable a new generation of experiments in hadronic nuclear physics, seeking to address fundamental questions in our understanding of QCD. The existence of exotic states, suggested by both quark models and lattice calculations, would allow gluonic degrees of freedom to be explored, and may help explain the role played by gluons in the QCD interaction. This article will review the meson spectroscopy program being planned at the lab following the 12 GeV upgrade, utilising real and quasi-real photon beams in two of the lab's four experimental halls, whose distinct capabilities will enable an extensive set of spectroscopy experiments to be performed at the same facility.


1989 ◽  
Vol 67 (12) ◽  
pp. 1228-1249 ◽  
Author(s):  
Jean Potvin

The numerical simulation of quantum chromodynamics on a space–time lattice allows for the calculation of many properties of hadronic matter at high temperature in a direct and in a nonperturbative fashion. This paper will be a review of the calculation techniques and results published in the past 5 years. Among other things, I will discuss the order of the phase transition, the critical temperature, the force between heavy quarks, as well as the thermodynamics and the spectroscopy of the quark–gluon plasma.


2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Pei-Lin Yin ◽  
Zhu-Fang Cui ◽  
Craig D. Roberts ◽  
Jorge Segovia

AbstractA symmetry-preserving treatment of a vector $$\times $$ ×  vector contact interaction is used to compute spectra of ground-state $$J^P = 0^\pm , 1^\pm $$ J P = 0 ± , 1 ± $$(f{\bar{g}})$$ ( f g ¯ ) mesons, their partner diquark correlations, and $$J^P=1/2^\pm , 3/2^\pm $$ J P = 1 / 2 ± , 3 / 2 ± (fgh) baryons, where $$f,g,h \in \{u,d,s,c,b\}$$ f , g , h ∈ { u , d , s , c , b } . Results for the leptonic decay constants of all mesons are also obtained, including scalar and pseudovector states involving heavy quarks. The spectrum of baryons produced by this chiefly algebraic approach reproduces the 64 masses known empirically or computed using lattice-regularised quantum chromodynamics with an accuracy of 1.4(1.2)%. It also has the richness of states typical of constituent-quark models and predicts many baryon states that have not yet been observed. The study indicates that dynamical, nonpointlike diquark correlations play an important role in all baryons; and, typically, the lightest allowed diquark is the most important component of a baryon’s Faddeev amplitude.


2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Mathieu Buchkremer ◽  
Alexander Schmidt

We review the theoretical and experimental situation for long-lived heavy quarks, or bound states thereof, arising in simple extensions of the Standard Model. If these particles propagate large distances before their decay, they give rise to specific signatures requiring dedicated analysis methods. In particular, vector-like quarks with negligible couplings to the three known families could have eluded the past experimental searches. While most analyses assume prompt decays at the production vertex, novel heavy quarks might lead to signatures involving displaced vertices, new hadronic bound states, or decays happening outside of the detector acceptance. We perform reinterpretations of existing searches for short- and long-lived particles, and give suggestions on how to extend their reach to long-lived heavy quarks.


1967 ◽  
Vol 31 ◽  
pp. 405
Author(s):  
F. J. Kerr

A continuum survey of the galactic-centre region has been carried out at Parkes at 20 cm wavelength over the areal11= 355° to 5°,b11= -3° to +3° (Kerr and Sinclair 1966, 1967). This is a larger region than has been covered in such surveys in the past. The observations were done as declination scans.


1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.


1961 ◽  
Vol 2 (2) ◽  
pp. 73-105 ◽  
Author(s):  
John R. W. Small

It is generally accepted that history is an element of culture and the historian a member of society, thus, in Croce's aphorism, that the only true history is contemporary history. It follows from this that when there occur great changes in the contemporary scene, there must also be great changes in historiography, that the vision not merely of the present but also of the past must change.


1962 ◽  
Vol 11 (02) ◽  
pp. 137-143
Author(s):  
M. Schwarzschild

It is perhaps one of the most important characteristics of the past decade in astronomy that the evolution of some major classes of astronomical objects has become accessible to detailed research. The theory of the evolution of individual stars has developed into a substantial body of quantitative investigations. The evolution of galaxies, particularly of our own, has clearly become a subject for serious research. Even the history of the solar system, this close-by intriguing puzzle, may soon make the transition from being a subject of speculation to being a subject of detailed study in view of the fast flow of new data obtained with new techniques, including space-craft.


1979 ◽  
Vol 46 ◽  
pp. 96-101
Author(s):  
J.A. Graham

During the past several years, a systematic search for novae in the Magellanic Clouds has been carried out at Cerro Tololo Inter-American Observatory. The Curtis Schmidt telescope, on loan to CTIO from the University of Michigan is used to obtain plates every two weeks during the observing season. An objective prism is used on the telescope. This provides additional low-dispersion spectroscopic information when a nova is discovered. The plates cover an area of 5°x5°. One plate is sufficient to cover the Small Magellanic Cloud and four are taken of the Large Magellanic Cloud with an overlap so that the central bar is included on each plate. The methods used in the search have been described by Graham and Araya (1971). In the CTIO survey, 8 novae have been discovered in the Large Cloud but none in the Small Cloud. The survey was not carried out in 1974 or 1976. During 1974, one nova was discovered in the Small Cloud by MacConnell and Sanduleak (1974).


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