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Title: Exotic particles with four or more quarks

Abstract

The familiar denizens of the particle zoo are made of two or three quarks, but particle theory allows for states comprising any number of those fundamental particles. Finally, after decades of searching, tetraquarks seem to have been spotted.

Authors:
Publication Date:
OSTI Identifier:
22303680
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics Today; Journal Volume: 67; Journal Issue: 9; Other Information: (c) 2014 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ELEMENTARY PARTICLES; HADRONIC ATOMS; QUARKS

Citation Formats

Olsen, Stephen Lars. Exotic particles with four or more quarks. United States: N. p., 2014. Web. doi:10.1063/PT.3.2525.
Olsen, Stephen Lars. Exotic particles with four or more quarks. United States. doi:10.1063/PT.3.2525.
Olsen, Stephen Lars. Mon . "Exotic particles with four or more quarks". United States. doi:10.1063/PT.3.2525.
@article{osti_22303680,
title = {Exotic particles with four or more quarks},
author = {Olsen, Stephen Lars},
abstractNote = {The familiar denizens of the particle zoo are made of two or three quarks, but particle theory allows for states comprising any number of those fundamental particles. Finally, after decades of searching, tetraquarks seem to have been spotted.},
doi = {10.1063/PT.3.2525},
journal = {Physics Today},
number = 9,
volume = 67,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}
  • Several models with more than four quarks are reviewed and compared with the four-quark model. They generally have right- and left-handed currents and are of the SU$sub 2$ x U$sub 1$ type. The lepton sectors are also discussed including the possibilities of heavy charged and neutral leptons. The weak phenomenology, triangle anomalies, degenerate quark masses, and radial excitations are examined. (AIP)
  • It is shown that the requirements of spontaneous CP breaking and natural flavor conservation lead to a class of theories where CP nonconservation is due solely to Higgs exchange, for an arbitrary number of fermion generations.
  • A search is presented for exotic decays of a Higgs boson into undetectable particles and one or two isolated photons in pp collisions at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of up to 19.4 inverse femtobarns collected with the CMS detector at the LHC. Higgs bosons produced in gluon-gluon fusion and in association with a Z boson are investigated, using models in which the Higgs boson decays into a gravitino and a neutralino or a pair of neutralinos, followed by the decay of the neutralino to a gravitino and a photon. The selectedmore » events are consistent with the background-only hypothesis, and limits are placed on the product of cross sections and branching fractions. Assuming a standard model Higgs boson production cross section, a 95% confidence level upper limit is set on the branching fraction of a 125 GeV Higgs boson decaying into undetectable particles and one or two isolated photons as a function of the neutralino mass. For this class of models and neutralino masses from 1 to 120 GeV an upper limit in the range of 7 to 13% is obtained. Further results are given as a function of the neutralino lifetime, and also for a range of Higgs boson masses.« less
  • A search is presented for exotic decays of a Higgs boson into undetectable particles and one or two isolated photons in pp collisions at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of up to 19.4 inverse femtobarns collected with the CMS detector at the LHC. Higgs bosons produced in gluon-gluon fusion and in association with a Z boson are investigated, using models in which the Higgs boson decays into a gravitino and a neutralino or a pair of neutralinos, followed by the decay of the neutralino to a gravitino and a photon. The selectedmore » events are consistent with the background-only hypothesis, and limits are placed on the product of cross sections and branching fractions. Assuming a standard model Higgs boson production cross section, a 95% confidence level upper limit is set on the branching fraction of a 125 GeV Higgs boson decaying into undetectable particles and one or two isolated photons as a function of the neutralino mass. For this class of models and neutralino masses from 1 to 120 GeV an upper limit in the range of 7 to 13% is obtained. Further results are given as a function of the neutralino lifetime, and also for a range of Higgs boson masses.« less
  • We measured the branching ratio [ital R] of [ital e][sup +][ital e][sup [minus]][r arrow]4[gamma] with respect to [ital e][sup +][ital e][sup [minus]][r arrow]2[gamma] as [1.48[plus minus]0.13(statistical)[plus minus]0.12(systemic)][times]10[sup [minus]6]. The upper limits of the branching ratios for the exotic particles are obtained to be around 3[times]10[sup [minus]7].