skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Triangle singularities and XYZ quarkonium peaks

Abstract

We discuss analytical properties of partial waves derived from projection of a 4-legged amplitude with crossed-channel exchanges in the kinematic region of the direct channel that corresponds to the XYZ peaks in charmonium and bottomonium. We show that in general partial waves can develop anomalous branch points in the vicinity of the direct channel physical region. In a specific case, when these branch points lie on the opposite side of the unitary cut they pinch the integration contour in a dispersion relation and if the pinch happens close to threshold, the normal threshold cusp is enhanced. We show that this effect only occurs if masses of resonances in the crossed channel are in a specific, narrow range. We estimate the size of threshold enhancements originating from these anomalous singularities in reactions where the $$Z_c(3900)$$ and the $$Z_b(10610)$$ peaks have been observed.

Authors:
 [1]
  1. Indiana Univ., Bloomington, IN (United States). Dept. of Physics and Center for Exploration of Energy and Matter; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States). Theory Center
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1198551
Alternate Identifier(s):
OSTI ID: 1184622
Report Number(s):
JLAB-THY-15-1999; DOE/OR/23177-3264; arXiv:1501.01691
Journal ID: ISSN 0370-2693; PII: S0370269315004517; TRN: US1601127
Grant/Contract Number:  
AC05-06OR23177; FG0287ER40365
Resource Type:
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 747; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Szczepaniak, Adam P. Triangle singularities and XYZ quarkonium peaks. United States: N. p., 2015. Web. doi:10.1016/j.physletb.2015.06.029.
Szczepaniak, Adam P. Triangle singularities and XYZ quarkonium peaks. United States. doi:10.1016/j.physletb.2015.06.029.
Szczepaniak, Adam P. Mon . "Triangle singularities and XYZ quarkonium peaks". United States. doi:10.1016/j.physletb.2015.06.029.
@article{osti_1198551,
title = {Triangle singularities and XYZ quarkonium peaks},
author = {Szczepaniak, Adam P.},
abstractNote = {We discuss analytical properties of partial waves derived from projection of a 4-legged amplitude with crossed-channel exchanges in the kinematic region of the direct channel that corresponds to the XYZ peaks in charmonium and bottomonium. We show that in general partial waves can develop anomalous branch points in the vicinity of the direct channel physical region. In a specific case, when these branch points lie on the opposite side of the unitary cut they pinch the integration contour in a dispersion relation and if the pinch happens close to threshold, the normal threshold cusp is enhanced. We show that this effect only occurs if masses of resonances in the crossed channel are in a specific, narrow range. We estimate the size of threshold enhancements originating from these anomalous singularities in reactions where the $Z_c(3900)$ and the $Z_b(10610)$ peaks have been observed.},
doi = {10.1016/j.physletb.2015.06.029},
journal = {Physics Letters. Section B},
number = ,
volume = 747,
place = {United States},
year = {2015},
month = {6}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1016/j.physletb.2015.06.029

Citation Metrics:
Cited by: 42 works
Citation information provided by
Web of Science

Save / Share: