Transcript QWG Meeting- Beijing 12

Meeting- Beijing
12-15 October 2004
Highlights of Future Opportunities
Stephen Godfrey
Carleton University, Canada
Miguel A. Sanchis-Lozano
IFIC - Valencia University, Spain
知之為知之，不知為不知，是知也。
QWG Beijing
M.A. Sanchis-Lozano IFIC
Valencia
When you know a thing,
maintain you know it;
when you do not,
acknowledge it.
This is the characteristic
of knowledge
Kong Fu Zi (Confucius)
1
Effective theories for quarkonium (I)
Theoretical Tools
NRQCD. Effective field theories have become a necessary tool to analyze the dynamics
of heavy quarkonium: a non-relativistic bound state with a hierarchy of scales.
Progress has to be made in two directions:
> Improving the perturbative series either by
- increasing the order of the calculation (in either αs or v) or
- resumming large contributions (renormalons or large logs)
> Improving the knowledge of the NRQCD matrix elements either by
- extracting numerical values by fitting exp data
- test of universality
- problem when linear combinations of ME appear
- universal shape functions to cope with non-perturbative effects
- direct evaluation via lattice calculations or models
Heavythe
quarkonium
far more complicated
- exploiting
hierarchy is
of something
scales in NRQCD
two quarks
each other
-than
Velocity
scaling“dancing”
rules to bearound
checked
pNRQCD. Remaining (ultrasoft) degrees of freedom: mv2 (to be compared with ΛQCD)
> Clarify assignations of heavy quarkonium states to dynamical regions
> Interest in performing renormalization group analysis (also vNRQCD)
- resummation of logs yields agreement with experiment in c 
- precise predictions for the ηb and Bc mass
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Effective theories for quarkonium (II)
Theoretical Tools
Lattice QCD In the quenched approximation the condition ma  1 can be realized
for the charm quark while bottom quark is at the borderline of present possibilities.
> Introducing an anisotropy (with a temporal lattice of smaller spacing)
> Charmonia have been examined on isotropic lattice with sea quarks
NRQCD can be formulated on the lattice improving its predicitive power. In the past,
many calculations have used the quenched approximation. Now, the MILC
Collaboration incorporates dynamical quarks, relying on
> Fast supercomputers and improved staggered fermions
> In the case of quarkonia finite mass effects are milder than in B and D mesons
Lattice determinations of QCD parameters:
> charm and bottom (MS) masses from bare lattice quark masses
SCET is an EFT appropriate when there are energetic particles moving with small
invariant mass, such as Xg near the endpoint region.
> CLEO measurements in inclusive (1S) radiative decays favor a small value for
the color-octet 1S0 and 3P0 matrix elements but the accuracy should be improved
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Spectroscopy
cc Sector
Foreseen (or confirmed?) observation of the hc (1P1) state (prior evidence from
pphcJ/yp is weak) through the decay chain y’hc+p0c+p0+ by E835 and CLEO-c.
Physical interest:
> Comparison with the 13PJ cog : test of the Lorentz nature of the confining potencial,
(e.g. through its spin-spin part)
> The hc mass is an important validation of Lattice QCD and NRQCD calculations
Charmonium D-wave states are predicted to lie above open charm threshold:
> 13D3,13D2,11D2 states close to the y(3770) mass, quite narrow and with prominent transitions
to lower c-cbar states.
Future possibilities:
> Eichtein, Lane and Quigg : B decay could be a good place to look for such states. Indeed,
in the near future B factories can produce charmonium states in B decays so far eluded
> Confirming evidence at Tevatron of the X(3872) [discovered by BELLE via the decay mode
X(3872)  J/ψ π+π- ] has shown the CDF and D0 discovery potential for new charmonium states
> BES III running at very high luminosity and sitting on the 43S1 and 53S1 states will allow to
observe radiative transitions to higher 2P, 3P, and possibly cascades to 2D and even 1F states.
> The observation of double charm opens up unique perspectives to study charm spectroscopy
(e.g. doubly charmed baryons) and production and decay dynamics
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Radiative and exclusive decays (I)
cc Sector
Radiative decays are not just useful pathways to other states but allow to probe details of
quarkonium wavefunctions and intrinsic properties (e.g. magnetic moment) and velocity
of heavy quarks in the bound state. Still poor known but relevant for NRQCD!
> CLEO-c has accumulated 1.5 million y(2S)’s allowing to study the single photon
spectrum and determine BR[y(2S)c(1S)]. A much larger sample is needed to
observe the direct transition to c(2S)
- the hindered transition will measure relativistic corrections (e.g. finite size), while
- the direct M1 transition will measure the magnetic moment of the charm quark
> Measurement of angular distributions in cc radiative decays gives insight into the
multipolar structure of the process:
- decay dominated by the E1 dipole term
- higher M2 and E3 transitions arise in a relativistic treatment.
- Comparison between E760 (cc2) and Crystal Ball (cc1) results are not consistent with
theory: additional contributions? Effect also seen by E835. More statistics needed!
Radiative decays of J/y into , ’ and c states can test the underlying dynamics:
> assumed to be dominated by the gluonic contribution
> of particular interest radiative quarkonium decays into scalar mesons instead of pseudoscalars
(they might even be glueballs with admixtures of light quarks)
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Radiative and exclusive decays (II)
cc Sector
Exclusive decays constitute an interesting laboratory for investigating corrections to the
leading-twist approach. A systematic study of such is lacking. For example,
> hadronic helicity conservation is violated in J/yVP decays
> longitudinally polarized vector mesons are forbidden in  cVV decays
> leading-twist forbidden cc BB decays have sizeable BF’s (diquark model?)
One important question to be answered is whether factorization holds to higher-twist
order, taking into account
> higher- Fock state contributions
> soft power corrections
Especially interesting is the so-called -p puzzle in J/y and y’ decays
> Intrinsic charm component? One of the most dramatic unsolved problems
> Other points: radiative decays into light hadrons, e.g. J/ψπ0
Recently, an enhancement near twice the proton mass was found by BES in the invariant
mass spectrum of the J/y decay into a proton-antiproton pair, providing evidence for a
bound state (not yet clear if a S- or a P-wave state).
> result close to the findings in pd and pp reactions and the BELLE observations in B decays
> Puzzling is however that no peak is seen in J/ypp. Suggestions by Rosner
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Spectroscopy …
bb Sector
So far no singlet state in the bottomonium family has been observed
> b(n1S0) states can be produced via M1 transitions from the (n3S1) states (either direct or
hindered) and via E1 radiative transitions from n1P1 states through a decay chain, e.g.
(3S)  hb(1P1) ππ, followed by hb b +  which is useful to observed the hb state too
> Another good chance to detect b’s is given to hadron colliders (through OZI suppressed
final states like J/ψ J/ψ, easy to identify through its muonic decay):
- at present Tevatron run
- with the next generation of B experiments, namely BTeV and LHC-b
> A promising opportunity is to turn the asymmetric B-factories into  factories during the
last fraction of their running period
M1 transitions have only been observed in the charmonium system. For bottomonium
CLEO sees no evidence for the hindered M1 transitions (3S)  b(1S),, (3S)  b(2S)
and (2S)  b(1S), ruling out a number of models. E1 transitions between (3S) and
Cb(2PJ ) states have been observed.
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… and decays
bb Sector
Hadronic transitions can be useful to complete our picture of heavy quark spectroscopy:
> HT’s can play a role in the search for hc and hb states.
Up to now a few HT processes have been observed in bottomonia (and charmonia).
To describe theoretically HT’s one can use chiral symmetry for light mesons and heavy
quark spin symmetry for the heavy states.
> progress to be made by using a relativistic coupled-channel approach
Check of lepton universality in leptonic decays of resonances: its possible breakdown
would inidicate new physics
> a virtual CP-odd Higgs boson could mediate the annihilation into a dilepton of an
intermediate b* state subsequent to a M1 transition of the  resonance
> as the soft photon would be undetected, this contribution would unwittingly
ascribed to the tauonic mode, thereby breaking lepton universality: signal of new physics
> Possible spectroscopic consequences
- b width larger than expected
- m-mb (hyperfine) splitting larger than expected
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t t Sector
Top quark pair production at threshold has many problems remaining to be solved:
> NNLL corrections (RG improved) corrections to the top pair production current
> complete fixed order (NNNLO) prediction of the total cross section
> conceptual issue: consistent treatment of EW corrections including instability of the top
quark and interferences with non-resonant final states
> rescattering corrections
Run II at the Tevatron and future LHC hadroproduction of t-tbar pairs are growing out of
the discovery era and entering the phase of precision measurement.
In a not too far future, an e+e- Linear Collider will be in operation.
> realistic simulations require the treatment of differential distributions, width and rscattering
effects as well as detector and beam effects
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Quark mass and as
Precise measurements
At ongoing and future B-physics experiments, the charm and bottom quark masses
and realistic estimates of their uncertainties will become increasingly important for the
measurements of CKM parameters and the search for new physics. However,
> due to confinement and non-perturbative aspects of the strong interaction the concept of
quark mass cannot be tied to an intuitive picture: as the weight or the rest mass of a body
> rather, it should be considered as the strong coupling constant as, depending on the
renormalization scheme and scale : pole mass, MS mass, threshold mass (kinetic, potential,
renormalon subtracted mass)…
> Different methods employed: sum rules, seminclusive B decays, lattice QCD
So far all numerical analyses based on non-relativistic quantities relied on fixed-order
perturbation theory.
> renormalization group improved calculations could be applied (already for the top quark)
> complementary approach based on quark and gluonj condensate beyond leading order
Heavy quarkonia leptonic and non-leptonic inclusive decay rates, in principle, provide means
to determine the strong coupling as using perturbative QCD, e.g.
> using the ratio Rm of the total hadronic decay and leptonic decay widths
> using lattice QCD
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cb Sector
Production. In contrast to flavor-hidden heavy quarkonia, the color-octet contributions
to Bc hadroproduction are expected to be small and the production cross section should
be mainly accounted for by the order-as4 color-singlet contribution, including feed-down
from excited S-wave states.
> If the Bc inclusive production, measured at the Tevatron or the LHC, comes to be larger than
the theoretical prediction, it could indicate that there is a larger contribution either from
higher states or color-octet mechanisms.
Spectroscopy. The bc system has a rich spectrum of excited states below BD threshold.
Once produced, these Bc mesons can only undergo radiative or hadronic transitions to the
ground state which then would decay weakly. For lattice QCD, the Bc mass is gold-plated.
Decays. Different competing modes: - c-quark decay with spectator b-quark (~70%)
- b-quark decay with spectator c-quark (~20%)
- annihilation (~10%)
> Measurements of the Bc lifetime should give information on the c- and b-quark mass
> Semi-leptonic decays can test the spin symmetry of NRQCD and HQET
> Also interesting the (destructive) interference of the bccs transition and the initial c-quark
> Study of CP-violation in order to extract the angle  in Bc decays
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Quarkonium hybrids
The existence of gluonic excitations in the hadron spectrum is one of the most important
unanswered questions in hadron physics. Hybrid meson: formed by a quark-antiquark
pair with an excited gluonic degree of freedom. Lattice gauge theory and hadron models
predict a rich spectroscopy of charmonium hybrids i.e. states non-consistent with the
constituent quark model
> JPC = 1-+ state: M(ψg) ~ 4 GeV , lying in the vicinity of D**D threshold: tantalizing possibility
of a relatively narrow state if below!
Charmonium hybrids can be produced and detected in B decays:
> B  ψg + X, BF[B  ψg(all JPC)+X] ~ 1% if M < 4.7 GeV
There are three important decay modes for charmonium hybrids:
( , ) ( , )
> Decays to D * ** D * ** : the challenge is to identify decay modes which can be exp reconstructed
> Decays to (ccbar)+(light hadrons): the cleanest signature if the BF is large enough, e.g.
ψg  (y, y’)+(light hadrons)
Kuang-Yan mechanism
Also radiative decays may be relevant, e.g.
ψg  (J/y,hc)+
E1 transition
> Decays to light hadrons: Offer the possibility of producing light exotic mesons
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Relativistic heavy ion program
In Media
Matter should undergo a transition to gluon quark plasma at high energy and temperature.
Hope to recreate matter as it was at the beginning of the Universe (“little bangs”): a hot
system with deconfined quarks and gluons and no chiral symmetry breaking. One of the
most prominent properties of this state of matter is the screening of color forces between
static quarks leading to quarkonium suppression in production mechanisms.
> Main experimental interest are RHIC and LHC where baryon density is relatively small and
temperature high: collect data in pA and Au-Au (and some other lighter AA) collisions
> Lattice QCD at finite temperature:
- What is the critical temperature at which quarkonium states dissociate?
- What is the influence of temperature on masses, dispersion relations and widths of quarkonium
- How big is the influence of light quarks?
- Which are the properties of strongly interacting matter near the deconfining transition?
- Analytic theoretical calculations: identify the dynamcial degrees of freedom and develop a
quantitative theory of quarkonium interactions with hot QCD matter
> Lattice QCD at zero temperature:
- What are the matrix elements of gluon and quark operators related to quarkonium dissociation ?
- Analytic theoretical calculations: relate expression for quarkonium dissociation amplitudes and
the matrix elements computed on the lattice
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First man-made
accelerator
(used by Galileo)
Charm factories
Experimental facilities
and projects
CLEO-c will collect high statistics running on the charmonium JPC=1-- resonances.
Already data taking on the y’(3686) allowing the following possibilities (3fb-1):
> Hadronic decays: search for the hc in y’p0hc and also for y’p (small BF)
> Detailed studies of cc1, cc2, cc3 : measurement of BF’s
> Radiative decays: BF’s of y’c y y’c’
> Exotica: radiative decays expected to be a prime source for glue rich final states
Physics at the y’’(3770) : Searches for rare decays like y’ppJ/y or the double cascade decay
y’’cc1,c2J/yl+l-.
> Information on 1D1/2S1 mixing sheding light into the X(3872) state which might be a 1D2 state.
Another important goal is to acquire ~109 events at the J/y(3097) peak:
> Search for gluonic excitations through the radiative decay: J/yX
> Prospects of making use of y’pлJ/y to tag J/y(3097), studying its final state polarization
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Charm factories
Experimental facilities
and projects
BEPC II / BES III will get a quite large luminosity (bordering a TCF): expected to be
completed by the end of 2006 and physics running in 2007. The feasibility report has been
officially approved by the Chinese government.
> Peak luminosity will be 1033cm-2s-1 at 1.89 GeV, two orders of magnitude higher than BEPC
The main physics goals are precision measurements and searches for new particles and
phenomena, mainly in the energy region from the J/ψ to ψ(3770). For example,
> D and Ds decays will allow the determination of CKM matrix elements with a few % precision
> A number of important physics topics in the t-charm region
> Precise measurement of R, to determine the charm mass with very small systematic uncertainty
> Search for new physics in charmonium and bottomonium decays:
- Possible lepton number (flavor) violation e.g. in J/ψ l l’ decays
- CP test with J/ψ decays (e.g. J/ψ  Λ Λ) probing the chromo-electric and magnetic
moments of charm quarks
BEPC will be upgraded to become
a double-ring collider
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B factories
Experimental facilities
and projects
B factories at SLAC and KEK should allow to study charmonium in B decays: the
bc cbar s subprocess is CKM-favoured.
Super-B factory : There is a proposal to upgrade KEKB to a Super KEKB with 5×1035
cm-2s-1 luminosity (a factor 50 of improvement!) along with the BELLE detector.
> Big challenges are the harsh background due to the high beam current and computing as
online data has to be recorded at a speed of 250 MB/sec.
The expected high statistics would provide the opportunity to discover
> hc and D-wave states: 13D3, 13D2 and 11D2
> charmonium hybrid states
> shed light on possible molecules formed by D and anti-D states
- it has been argued that the X(3872) state might be a DD* molecule
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Hadron colliders
Experimental facilities
and projects
Tevatron. High-luminosity Run II is in progress. The recorded and future large statistics
will be used for:
> Production Studies:
- production differential cross sections up to at least pT = 30 GeV/c
- cross sections for direct production of quarkonium states
- with increased statistics it might be possible to access charmonium states as
c and hc(nP)
- polarization studies (test of NRQCD factorization)
- associated production of J/ψ, ψ(2S),…, e.g. double J/ψ production or in association
with ccbar
> Decay Studies:
- X(3872)  J/ψπ+π- ; decay ME’s dependence on the ππ invariant mass
- hadron decays into charmonia, e.g. exclusive B decays into final states involving J/ψ
- Bc studies (mass and lifetime)
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Hadron colliders
Experimental facilities
and projects
GSI (at Darmstadt - Germany) will produce charmonium in proton-antiproton collisions
and can be considered as an extension of the successful experiments performed at
the Fermilab antiproton accumulator. Two modes of operation are foreseen:
> high luminosity with peaks of 2 x 1032 cm-2s-1 (using stochastic cooling)
> reduced luminosity 1031 cm-2 s-1
The PANDA detector must provide (nearly) full solid angle coverage with good
particle identification and momentum resolution for , e, μ , π, K and p.
An intensive spectroscopy program improving considerably the statistics
will be carried out.
> Ground state of charmonium and its radial excitation
> hc resonance of charmonium
> charmonium hybrids
> charmonium in nuclei
> charmonium above open charm threshold
. Unlike e+e- colliders at GSI all quantum numbers are directly accessible.
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Hadron colliders
Experimental facilities
and projects
LHC (ATLAS/CMS) scheduled to start in 2007 will provide many opportunities for
heavy quarkonia, though the huge hadronic background will make spectroscopy studies
difficult. The initial luminosity L=2x1033cm-2s-1 is well suited for dedicated studies on
heavy quarkonia: affordable trigger rates, modest pile-up … However, in view of tight
funding constraints (with changes in detector geometry and luminosity…) the initially
foreseen scenario has to be revised (studies still going-on but first results promising)
> Production rates of heavy flavors will be huge
- For heavy quarkonia, the di-muon trigger will be the most important one, allowing
for an effective selection of channels with J/ψ or  via their muonic decay mode.
Study of HQ hadroproduction. One of the first measurements at the LHC will be
the direct J/ψ and  production cross sections:
> Extraction of NRQCD matrix elements
> Test of NRQCD factorization: polarization of J/ψ and  resonances at large pT
Bc studies. Large production rates will allow for precision measurements of Bc properties
> lifetime, mass …
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Hadron colliders
Experimental facilities
and projects
LHC-b detector is designated to exploit the large number of b-hadrons produced at LHC,
with excellent vertex resolution and particle identification for charged particles.
> precision studies of CP
> rare decays of B-mesons
> Bc meson decays including radiative Bc* decays
ALICE is a dedicated heavy ion experiment at the LHC. The detector is designed to cope
with large particle multiplicities (between 2000 and 8000 per unit rapidity in central Pb-Pb
collisions). The aim of ALICE is to investigate the properties of strongly interacting matter at
extreme energy density where the formation of quark-gluon plasma is expected.
> The (1S) is expected to dissolve above the critical temperature
- the spectroscopy of the  family at LHC energies should reveal unique information on QGP
> Significant differences wrt lower energies (leading to enhancement rather then suppression)
- charmonia produced from bottom decay, D antiD annihilation and coalescence mechanisms
> Open charm/beauty production should provide a natural normalization to observe suppression
Charmonia production in proton-nucleus collisions. NA60 has proposed to clarify
questions made by previous SPS experiments, e.g.
> J/ψ production suppressed in heavy-ion collisions wrt proton-nucleus collisions
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CONCLUSIONS
Historically quarkonium physics has played a fundamental role in the
development of Quantum Chromodynamics.
In recent times once again it has become one of the most active areas of
subatomic physics with the discovery of several new states: 13DJ(bb) states
by CLEO, c’ by Belle (subsequently confirmed by CLEO and Babar) and the
yet mysterious X(3872) charmonium state first seen by Belle in B-decay
and then observed by CDF and D0 at the Tevatron and Babar in B-decay.
Many questions remain unanswered and experimental progress goes hand in
hand with theoretical developments.
Moreover, high precision studies will allow the search for new physics in a
variety of issues involving heavy quarkonium
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In sum, progress in quarkonium physics should come from the interplay
between theory and experiment from quite different places.
THANK YOU !
Very important to keep
people in touch!
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