Sinead M. Ryan

Publications (26)4.56 Total impact

• Article: Excited spectroscopy of charmed mesons from lattice QCD

  Graham Moir, Michael Peardon, Sinead M. Ryan, Christopher E. Thomas, Liuming Liu
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  ABSTRACT: We present spectra of highly excited D and Ds mesons up to around 3.8 GeV determined using dynamical lattice QCD. We employ novel computational techniques and the variational method with a large basis of carefully constructed operators in order to extract and reliably identify the continuum spin of an extensive set of excited states. These include states with high spin and states identified as having an explicit gluonic contribution. Calculations were performed on two volumes, both with a pion mass of approximately 400 MeV, achieving a high statistical precision for both ground and excited states. We discuss our results in light of experimental observations, comment on the phenomenological implications and identify the lightest `supermultiplet' of hybrid mesons in each sector.
  01/2013;
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  Available from: Graham Moir

  Article: Excited $D$ and $D_{s}$ meson spectroscopy from lattice QCD

  Graham Moir, Michael Peardon, Sinead M. Ryan, Christopher E. Thomas
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  ABSTRACT: We present highly excited spectra of charm-light and charm-strange mesons from dynamical lattice QCD. Our calculations are performed on anisotropic $N_{f} = 2+1$ dynamical ensembles generated by the Hadron Spectrum Collaboration. The use of novel techniques and a large basis of interpolating operators have allowed us to extract these spectra to a high degree of statistical precision, extract states of high spin and observe candidate hybrid mesons. We interpret and discuss our results in light of the current experimental situation.
  01/2013;
• Article: Two topics from lattice NRQCD at non-zero temperature: heavy quark mass dependence and S-wave bottomonium states moving in a thermal bath

  Seyong Kim, Gert Aarts, Chris Allton, Maria Paola Lombardo, Mehmet B. Oktay, Sinead M. Ryan, Donald K. Sinclair, Jon-Ivar Skullerud
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  ABSTRACT: Using Non-Relativistic QCD (NRQCD), we study heavy quark mass dependence of S-wave and P-wave bottomonium correlators for 0.42Tc <= T <= 2.09Tc and study spectral functions of S-wave bottomonium states moving in a thermal bath at these temperatures using Maximum Entropy Method with NRQCD kernel. For the studied momentum range, the energy of moving states shows quadratic momentum-dependence and the width of moving states does not show significant changes as the momentum of bottomonium is increased. Also, we find that in correlator ratios, the temperature effect is larger than the effect caused by 20% change in the bottom quark mass.
  10/2012;
• Article: S wave bottomonium states moving in a quark-gluon plasma from lattice NRQCD

  Gert Aarts, Chris Allton, Seyong Kim, Maria Paola Lombardo, Mehmet B. Oktay, Sinead M. Ryan, D. K. Sinclair, Jon-Ivar Skullerud
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  ABSTRACT: We extend our study of bottomonium spectral functions in the quark-gluon plasma to nonzero momentum. We use lattice QCD simulations with two flavours of light quark on highly anisotropic lattices and treat the bottom quark with nonrelativistic QCD (NRQCD). We focus on S wave (Upsilon and eta_b) channels and consider nonrelativistic velocities, v/c < 0.2. A comparison with predictions from effective field theory is made.
  10/2012;
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  Available from: Graham Moir

  Article: Charmonium spectroscopy from an anisotropic lattice study

  Liuming Liu, Sinead M. Ryan, Mike Peardon, Graham Moir, Pol Vilaseca
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  ABSTRACT: We present a progress report on our study of the charmonium spectrum in full QCD on anisotropic lattices generated by the Hadron Spectrum Collaboration. We adopt a large basis of interpolating operators to extract the excited charmonium states using the variational method. A detailed spectrum of excited charmonium mesons in many $J^{PC}$ channels is obtained. Hybrid states with exotic and non-exotic quantum numbers are determined and preliminary results from a study of disconnected contributions to the $\eta_c$ are presented.
  12/2011;
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  Available from: Jon-Ivar Skullerud

  Article: What happens to the Upsilon and eta_b in the quark-gluon plasma? Bottomonium spectral functions from lattice QCD

  Gert Aarts, Chris Allton, Seyong Kim, Maria Paola Lombardo, Mehmet B. Oktay, Sinead M. Ryan, D. K. Sinclair, Jon-Ivar Skullerud
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  ABSTRACT: We study bottomonium spectral functions in the quark-gluon plasma in the Upsilon and eta_b channels, using lattice QCD simulations with two flavours of light quark on highly anisotropic lattices. The bottom quark is treated with nonrelativistic QCD (NRQCD). In the temperature range we consider, 0.42 < T/T_c < 2.09, we find that the ground states survive, whereas the excited states are suppressed as the temperature is increased. The position and width of the ground states are compared to analytical effective field theory (EFT) predictions. Systematic uncertainties of the maximum entropy method (MEM), used to construct the spectral functions, are discussed in some detail.
  09/2011;
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  Available from: Jon-Ivar Skullerud

  Article: Bottomonium at Non-zero Temperature from Lattice Non-relativistic QCD

  Gert Aarts, Chris Allton, Seyong Kim, Maria Paola Lombardo, Mehmet B. Oktay, Sinead M. Ryan, D. K. Sinclair, Jon-Ivar Skullerud
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  ABSTRACT: The temperature dependence of bottomonium states at temperatures above and below $T_c$ is presented, using non-relativistic dynamics for the bottom quark and full relativistic lattice QCD simulations for two light flavors on a highly anisotropic lattice. We find that the S-waves ($\Upsilon$ and $\eta_b$) show little temperature dependence in this range while the P wave propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behavior consistent with nearly-free dynamics at approximately twice the critical temperature.
  09/2011;
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  Available from: Colin Morningstar

  Article: Excited-Nucleon Spectroscopy with 2+1 Fermion Flavors

  Saul Cohen, John M. Bulava, Justin Foley, Colin Morningstar, Ricky Wong, Robert G. Edwards, Balint Joo, David G. Richards, K. Jimmy Juge, Huey-Wen Lin, Nilmani Mathur, Michael J. Peardon, Sinead M. Ryan
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  ABSTRACT: We present progress made by the Hadron Spectrum Collaboration (HSC) in determining the tower of excited nucleon states using 2+1-flavor anisotropic clover lattices. The HSC has been investigating interpolating operators projected into irreducible representations of the cubic group in order to better calculate two-point correlators for nucleon spectroscopy; results are published for quenched and 2-flavor anisotropic Wilson lattices. In this work, we present the latest results using a new technique, distillation, which allows us to reach higher statistics than before. Future directions will be outlined at the end. Comment: 7 pages, 3 figures. Presented at the XXVII International Symposium on Lattice Field Theory, July 26-31, 2009, Peking University, Beijing
  11/2009;
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  Available from: ArXiv

  Article: Radial and orbital excitations of static-light mesons

  Justin Foley, Alan O'Cais, Sinead M. Ryan, Mike Peardon
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  ABSTRACT: We present results for the spectrum of static-light mesons from Nf=2 lattice QCD. These results were obtained using all-to-all light quark propagators on an anisotropic lattice, yielding an improved signal resolution when compared to more conventional lattice techniques. With a light quark mass close to the strange quark, we have measured the splittings between the ground-state S-wave static-light meson and higher excitations. We attempt to identify the quantum numbers of the excited states in the context of the reduced spatial symmetries of the lattice.
  03/2007;
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  Available from: arxiv.org

  Article: Static-light mesons on a dynamical anisotropic lattice

  Justin Foley, Alan O Cais, Mike Peardon, Sinead M. Ryan
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  ABSTRACT: We present results for the spectrum of static-light mesons from Nf=2 lattice QCD. These results were obtained using all-to-all light quark propagators on an anisotropic lattice, yielding an improved signal resolution when compared to more conventional lattice techniques. In particular, we consider the inversion of orbitally-excited multiplets with respect to the `standard ordering', which has been predicted by some quark models.
  11/2006;
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  Available from: Jon-Ivar Skullerud

  Article: Dynamical QCD simulations on anisotropic lattices

  Richie Morrin, Alan O Cais, Mike Peardon, Sinead M. Ryan, Jon-Ivar Skullerud
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  ABSTRACT: The simulation of QCD on dynamical (Nf=2) anisotropic lattices is described. A method for nonperturbative renormalisation of the parameters in the anisotropic gauge and quark actions is presented. The precision with which this tuning can be carried out is determined in dynamical simulations on 8^3x48 and 8^3x80 lattices.
  05/2006;
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  Available from: Jon-Ivar Skullerud

  Article: Static-light hadrons on a dynamical anisotropic lattice

  Justin Foley, Alan O Cais, Mike Peardon, Sinead M. Ryan, Jon-Ivar Skullerud
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  ABSTRACT: We present preliminary results for the static-light meson and baryon spectra for $N_f=2$ QCD. The study is performed on an anisotropic lattice and uses a new all-to-all propagator method allowing us to determine particle masses to a high precision.
  12/2005;
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  Available from: Jon-Ivar Skullerud

  Article: Practical all-to-all propagators for lattice QCD

  Justin Foley, K. Jimmy Juge, Alan O'Cais, Mike Peardon, Sinead M. Ryan, Jon-Ivar Skullerud
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  ABSTRACT: A new method for computing all elements of the lattice quark propagator is proposed. The method combines the spectral decomposition of the propagator, computing the lowest eigenmodes exactly, with noisy estimators which are 'diluted', i.e. taken to have support only on a subset of time, space, spin or colour. We find that the errors are dramatically reduced compared to traditional noisy estimator techniques.
  06/2005;
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  Available from: Jon-Ivar Skullerud

  Article: Static-light matrix elements on a dynamical anisotropic lattice

  K. Jimmy Juge, Richie Morrin, Alan O Cais, Mike Peardon, Sinead M. Ryan, Jon-Ivar Skullerud
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  ABSTRACT: The static-light matrix element needed to determine $f_B$ is studied on an anisotropic lattice with $N_f=2$. The improvement in precision due to stout links and all-to-all propagators is investigated.
  11/2004;
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  Available from: ArXiv

  Article: A perturbative determination of the parameters of an anisotropic quark action

  Justin Foley, Mike Peardon, Sinead M. Ryan
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  ABSTRACT: The parameters of a 3+1 anisotropic quark action with Symanzik-improved glue are determined at 1-loop in perturbation theory.
  11/2004;
• Source

  Available from: Jon-Ivar Skullerud

  Article: Improving Algorithms to Compute All Elements of the Lattice Quark Propagator

  Alan O Cais, K. Jimmy Juge, Mike J. Peardon, Sinead M. Ryan, Jon-Ivar Skullerud
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  ABSTRACT: We present a new exact algorithm for estimating all elements of the quark propagator. The advantage of the method is that the exact all-to-all propagator is reproduced in a large but finite number of inversions. The efficacy of the algorithm is tested in Monte Carlo simulations of Wilson quarks in quenched QCD. Applications that are difficult to probe with point propagators are discussed.
  10/2004;
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  Available from: arxiv.org

  Article: A non-perturbative study of the action parameters for anisotropic-lattice quarks

  Justin Foley, Alan O Cais, Mike Peardon, Sinead M. Ryan
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  ABSTRACT: A quark action designed for highly anisotropic lattice simulations is discussed. The mass-dependence of the parameters in the action is studied and the results are presented. Applications of this action in studies of heavy quark quantities are described and results are presented from simulations at an anisotropy of six, for a range of quark masses from strange to bottom.
  06/2004;
• Article: TRINLAT-03/03 , UPRF-2003-17 Non-perturbative study of QCD on a 2 + 2 anisotropic lattice

  Alessandra Feo, Mike Peardon, Sinead M. Ryan
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  ABSTRACT: INTRODUCTION QCD on 3+1 anisotropic lattices [1,2,3] has proved to be a successful tool for the nonperturbative investigation of interesting physical phenomema including the glueball spectrum, b b states, gluon strings, the spectral density. The method is successful for processes where the hadronic final state is static in the center of mass frame but it is perhaps less advantageous for processes in which the hadron momentum in the final state is non-negligible compared to its mass. In such cases, independent fine spatial directions for each momentum degree of freedom are needed to describe the system precisely. This increases dramatically the computational cost and, when considering an anisotropic approach, the di#culties linked with tuning the parameters. For processes where the final state hadron is strongly peaked at a momentum approximately equal to its mass, a 2+2 lattice discretization may provide a solution. It o#ers the possibility to extend the range of final state momenta
  06/2004;
• Article: TRINLAT-03/04 , UPRF-2003-19 The 2 + 2 anisotropic Wilson gluon action with applications

  Alessandra Feo, Mike Peardon, Sinead M. Ryan
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  ABSTRACT: tinuum limit theory is not guaranteed since there are two free parameters and a single ratio of scales. In order to ensure the re- Talk given by Alessandra Feo covery of the Euclidean invariance in the continuum limit the relative weights between the three operators must be determined to ensure Lorentz invariance in on-shell Green functions. This fine tuning must be fixed, either non-perturbatively [3] or perturbatively. We focus here on the perturbative approach. We follow the notation of Ref. [4] and first concentrate in the pure gluon sector of the SU(N c ) Yang-Mills theory. The action reads, S g = # x,,# c # [1 - Tr (P# (x) + P # (x))] (1) where the one-loop coe#cients, c # can be parametrized as (2+2) # # # ff g )) f-f 1 + # ) c-f 2 (1 + # (2) for 2+2 and (3+1) #(1 + # )) c-f + O(g (3) for 3+1. These three parameters must be tuned in order to restore the on-shell Lorentz invariance. At tree-level it is easy to de
  05/2004;
• Source

  Available from: tcd.ie

  Article: TRINLAT-03/05 Heavy hadrons on an anisotropic lattice

  Justin Foley, Alan O Cais, Mike Peardon, Sinead M. Ryan
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  ABSTRACT: me is now quite simple. An improved discretisation is only needed for the # i D i term in Eq. 3 since the simplest discretisation would lead to O(a s ) errors. Including the gauge fields and the meanlink improvement coe#cients, u s and u t the lattice fermion matrix reads ML x = a t ## r ma t + 18s + r + t g x 2u t (r - # 0 )U t (x) x+ t + (r + # 0 )U t (x - t) x- t (4s - r # i )U i (x) x+ + (4s + 2 i (x - ) x- (s - r # i )U i (x)U i (x + ) x+2 (4) (s + 1 i (x - )U i (x - 2) x-2 ## . Choosing r = 1 and s = 1/8 yields the sD34 action proposed in Ref [1]. The authors investigated the radiative corrections to this action and at one-loop in perturbation theory find no contribution from O(# s a s m q ) terms, which would spoil simulations with heavy quarks. This is a key advantage of this action over anisotropic SW- or D234-type actions where such terms may appear, depending on the choice of the parameter, r [2]. 2. R
  05/2004;