School of Mathematics
http://hdl.handle.net/2262/1
School of Mathematics2016-02-12T01:25:09ZSpectroscopy of doubly charmed baryons from lattice QCD
http://hdl.handle.net/2262/74473
Spectroscopy of doubly charmed baryons from lattice QCD
FERREIRA, MAURO
We present the ground and excited state spectra of doubly charmed baryons from lattice QCD with dynamical quark fields. Calculations are performed on anisotropic lattices of size 163×128, with inverse spacing in temporal direction at-1=5.67(4)GeV and with a pion mass of about 390 MeV. A large set of baryonic operators that respect the symmetries of the lattice yet which retain a memory of their continuum analogues are used. These operators transform as irreducible representations of SU(3)F symmetry for flavor, SU(4) symmetry for Dirac spins of quarks and O(3) for spatial symmetry. The distillation method is utilized to generate baryon correlation functions which are analyzed using the variational fitting method to extract excited states. The lattice spectra obtained have baryonic states with well-defined total spins up to 7/2 and the pattern of low-lying states does not support the diquark picture for doubly charmed baryons. On the contrary the calculated spectra are remarkably similar to the expectations from models with an SU(6)×O(3) symmetry. Various spin-dependent energy splittings between the extracted states are also evaluated.
PUBLISHED
2015-01-01T00:00:00ZCacti and filtered distributive laws
http://hdl.handle.net/2262/73949
Cacti and filtered distributive laws
DOTSENKO, VLADIMIR
Motivated by the second author’s construction of a classifying space for the group of
pure symmetric automorphisms of a free product, we introduce and study a family of
topological operads, the operads of based cacti, defined for every pointed simplicial
set
.
Y
;
p
/
. These operads also admit linear versions, which are defined for every
augmented graded cocommutative coalgebra
C
. We show that the homology of the
topological operad of based
Y
–cacti is the linear operad of based
H
.
Y
/
–cacti. In
addition, we show that for every coalgebra
C
the operad of based
C
–cacti is Koszul.
To prove the latter result, we use the criterion of Koszulness for operads due to the
first author, utilising the notion of a filtered distributive law between two quadratic
operads. We also present a new proof of that criterion, which works over a ground
field of arbitrary characteristic
PUBLISHED
2015-01-01T00:00:00ZQuark-gluon plasma phenomenology from the lattice
http://hdl.handle.net/2262/73781
Quark-gluon plasma phenomenology from the lattice
RYAN, SINEAD
The FASTSUM Collaboration has calculated several quantities relevant for QCD studies
at non-zero temperature using the lattice technique. We report here our results for the (i)
interquark potential in charmonium; (ii) bottomonium spectral functions; and (iii) electrical
conductivity. All results were obtained with 2+1 flavours of dynamical fermions on an
anisotropic lattice which allows greater resolution in the temporal direction.
PUBLISHED
2014-01-01T00:00:00ZThe bottomonium spectrum at finite temperature from N f = 2 + 1 lattice QCD
http://hdl.handle.net/2262/73780
The bottomonium spectrum at finite temperature from N f = 2 + 1 lattice QCD
RYAN, SINEAD
We present results on the bottomonium spectrum at temperatures above and
below the deconfinement crossover temperature,
T
c
, from dynamical lattice QCD simu-
lations. The heavy quark is treated with a non-relativistic effective field theory on the
lattice and serves as a probe of the hot medium. Ensembles with a finer spatial lattice
spacing and a greater range of temperatures below
T
c
than those previously employed by
this collaboration are used. In addition, there are
N
f
= 2 + 1 flavours of Wilson clover
quark in the sea with
M
π
≈
400 MeV and we perform a more careful tuning of the bottom
quark mass in this work. We calculate the spectral functions of S and P wave bottomonium
states using the maximum entropy method and confirm earlier findings on the survival of
the ground state S wave states up to at least 2
T
c
and the immediate dissociation of the
P wave states above
T
c
PUBLISHED
2014-01-01T00:00:00Z