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SUMMARY:Scattering Amplitudes and Resonance Properties from Lattice QCD
DTSTART;VALUE=DATE-TIME:20180827T060000Z
DTEND;VALUE=DATE-TIME:20180831T160000Z
DTSTAMP;VALUE=DATE-TIME:20180716T023411Z
UID:indico-event-133@cern.ch
DESCRIPTION:\n\n[from D. R. Bolton\, R. A. Briceño\, D. J. Wilson\, Phy
s. Lett. B757 (2016) 50-56\, arXiv:1507.07928]\n\nFigure 1: Postdiction o
f the ππ → ππ scattering phase in the ρ channel\, made by fitting L
QCD data at heavier pion masses using unitarized chiral perturbation theor
y (ChPT)\, and then extrapolating to the physical pion mass.\n \n\nIn rec
ent years\, Lattice QCD (LQCD) calculations of stable-hadron properties
have become considerably more precise\, and as a result\, LQCD inputs ar
e having an increasing impact on Standard-Model phenomenology. Considerin
g this progress\, it is natural to also examine the prospects for using la
ttice QCD to calculate the properties of unstable hadrons\, i.e. QCD reso
nances that decay via the strong force. The extraction of resonance proper
ties is much more challenging\, but also in this sector enormous progress
has been made in the development of both theoretical methods and numerical
techniques. A major focus here is the approach\, pioneered by Lüscher\,
of relating finite-volume energies to infinite-volume scattering observab
les. [See\, for example\, Figure 1.]\n\nThe long-term goal is to use LQCD
to study various exotic resonances\, including the recently-discovered X\
, Y and Z states as well as excited nucleon states\, including the Roper
resonance\, which decays predominantly to Nπ and Nππ.\n\n\n\n[J. Bulava
\, B. Hörz\, B. Fahy\, K. J. Juge\, C. Morningstar\, C. H. Wong\, PoS LAT
TICE2015 069\, arXiv:1511.02351]\n\nFigure 2: The time-like pion form fac
tor\, as determined in a LQCD calculation with mπ ∼ 240 MeV. The curve
corresponds to a Gounaris-Sakurai parameterization with the ρ-resonance m
ass and the ρππ coupling determined from the lattice data.\n\nBeyond ex
tracting QCD resonance properties\, one can also use the relation between
finite- and infinite-volume matrix elements to study electroweak transitio
ns. Applying these methods will allow one to extract resonance form facto
rs and to perform precision tests of the Standard Model. For instance\, pr
ocesses such as B → K* (di-lepton) → Kπ (di-lepton) are particularly
important for LHCb phenomenology. Another example is the time-like pion f
orm factor\, which can be related to the low-energy electron-positron anni
hilation cross section and represents a crucial input quantity for the de
termination of the hadronic-vacuum-polarization contribution to the anomal
ous magnetic moment of the muon\, (g − 2)μ. Formalism for extracting th
is quantity from LQCD is understood and numerical calculations are underwa
y [See Figure 2].\n\nThe aim of this workshop is to bring together expert
s in developing the formalism and lattice practitioners\, in order to revi
ew the status of ongoing calculations and discuss future prospects. The wo
rkshop will emphasize the future role of LQCD in precision resonance physi
cs\, especially in the context of forthcoming experiments.\n\nhttps://indi
co.mitp.uni-mainz.de/event/133/
LOCATION:Mainz Institute for Theoretical Physics\, Johannes Gutenberg Univ
ersity 02.430
URL:https://indico.mitp.uni-mainz.de/event/133/
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