Extraction of SM parameters
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Extraction of SM parameters
Onia and QCD
Onia Scales and QCD Effective Field Theories
Extraction of alpha_s and m_Q
Other examples
Open challenges in theory and experiments
What’s more?
Nora Brambilla (U. Milano)
from Onia
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QCD and the Onia
Parameters:
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QCD and the Onia
Parameters:
in some scheme and at some scale
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QCD and the Onia
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QQ: a multiscale System
and
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Non-relativistic bound states
Difficult alsofor the lattice!
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Disentangling scales with EFTs
Hard
Soft(relative
momentum)
Ultrasoft (binding energy)
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EFTs for Quarkonium
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NRQCD
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Weakly coupled pNRQCD
Pineda, Soto 97 Brambilla Pineda Soto Vairo 99
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In this framework we can obtain
Precision determinations of QCD parameters (of interest for SM and BSM physics)
information on QCD vacuum and low energy properties (of interest for theories beyond QCD)
information on the transition region from high energy to low energy (of interest for the behaviour of perturbative series)
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Low energy (nonperturbative) effects always existbut their form depend on the size of the system
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To extract SM parameters
consider systems or observables with suppressed nonperturbative effects
(typically quarkonia with small radius)
get under control the perturbative series and resum all large contributions
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Mass determination
Example: mass extraction from 1S energy level (e.g. Y(1s))
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Calculate QQ energies at best possible accuracy
perturbative singlet potential
singlet singletoctet
low energy gluon
•1)Sum large beta0 (removing the renormalon of the series) Beneke et al., Hoang et al.,Brambilla et al, Pineda
•2)Sum the logs of v (coming from the ratio of
scales:mv^2/mv, mv/m) RG correlated scales Luke and Savage;
Manohar and Stewart; Pineda Soto
•3) Deal with the nonperturbative corrections
Take n=1S, to obtain a precise extraction for the mass one has to:
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Static singlet potential 1)Bad behaviour of the perturbative series (the renormalon
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Static singlet potential
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1)Bad behaviour of the perturbative series (the renormalon
It was found that (Hoang et al., Pineda 99)
Is well behaved (the renormalon cancels between the two when one eliminates m_pole in terms of msbar or threshold mass)
main obstacle to precise extractions!
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1)after renormalon cancellation one gets a well behaved series and good agreement with the lattice:
2)large logs of v are RG resummed--> great improvement in stability and scale independence
(LL, NLL, NNLL...)
3)nonperturbative corrections are neglected (when suppressed)
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QWG Cern YR 2005hep-ph/0412158
Bottom mass extractions from Y(1S), Sum rules, lattice
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QWG Cern YR 2005hep-ph/0412158
Charm mass extraction from J/psi, sum rules, lattice
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NR Sum Rules (full NLL ,partial NNLL accuracy):
semileptonic B decays
lattice (unquenched)
Pineda Signer 06
Hoang Manohar 05
Gray et al 05
More recent determinations:
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alpha_s determination
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from PDG06
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Upsilondecay
Running of from PDG06
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New extraction of (Brambilla, Garcia, Soto, Vairo 07)
from
based on:
•new data from CLEO (hep-ex/0512061)
•Combined use of NRQCD, pNRQCD and SCET
•accurate estimates of the octet contributions from the lattice (bodwin, lee, Sinclair 05) and from
continuum (Garcia, Soto 05)
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Using NRQCD decay factorization:
we obtain
accurate at NLO in alpha_s and v
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We obtain
corresponding to
main uncertainty from systematic error in
discussion of previous determinations CLEO/PDG
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the new determination of alpha_s will move up the alpha_s average!
The alpha_sfrom quarkonium is now consistent
with the other determinations
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M1 Transitions
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radiative transitions
Magnetic Dipole transitions
In potential models
Eichten QWG 02
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EFTheory of radiative transitions
•No nonperturbative physics at order
•Exact relations from Poincare invariance
•No large anomalous magnetic moment
pNRQCD with singlet, octet, US gluons and photonsBrambilla, Jia, Vairo 05
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Improvement requires:
QWG extraction of c and b mass (2005)
For 1S mass extraction: Lattice calculation of <E E(t)> (full NNNLO and LL in pert)
In NRSM: -NNLL and NNNLO; for low moments SR, from
experiments: R for bb above threshold, new R for cc is good input
For lattice: th error in lattice -->MS conversion, need 2 loop matching in NRQCD and Fermilab;
nonperturbative matching desirable
Outlook: bottom and charm masses
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ttbar system: extraction of m_t at the ILC.Present undetermination around 100 MeV.
Needed: complete NNLL and complete NNNLO; EW and non fact.; EFT for unstable particles
From hyperfine separation calculated at NLL:
alphas da j/psi ->gamma Xneed both theory calculations and
experimental measurement
Outlook: top mass and alphas
alphas from etab
from a measurement of eta_b with few Mev accuracy get alpha_s(M_z) with 0.003 error!
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OutlookEffective field theories provide a systematic tool to investigate a wide range of heavy quark observables inside QCD
They need to be complemented by lattice calculations
These theory tools can match some of the intense experimental progress of the last few years and of the near future, but more has to be done:
Heavy quark bound states are a unique lab for the study of the strong interactions from the high energy scales where precision studies can be made to the low energy region whereconfinement and nonperturbative physics are dominant
Perturbative calculations at higher order(fixed order and logs summation)Lattice calculations of local and nonlocal condensates(or equivalently NRQCD matrix elements)
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backup slides
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Under search at Fermilab and CLEO
eta_b
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