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Title: Meeting-%20Beijing%2012-15%20October%202004


1
Meeting- Beijing12-15 October 2004
Highlights of Future Opportunities
  • Stephen Godfrey
  • Carleton University, Canada
  • Miguel A. Sanchis-Lozano
  • IFIC - Valencia University, Spain

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)
?????,?????,????
2
Theoretical Tools
Effective theories for quarkonium (I)
  • 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
  • gt Improving the perturbative series either
    by
  • - increasing the order of the calculation
    (in either as or v) or
  • - resumming large contributions
    (renormalons or large logs)
  • gt 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
  • - exploiting the hierarchy of
    scales in NRQCD
  • - Velocity scaling
    rules to be checked

Heavy quarkonium is something far more
complicated than two quarks dancing around
each other
pNRQCD. Remaining (ultrasoft) degrees of
freedom mv2 (to be compared with ?QCD) gt
Clarify assignations of heavy quarkonium states
to dynamical regions gt Interest in
performing renormalization group analysis (also
vNRQCD) - resummation
of logs yields agreement with experiment in ?c
??? - precise
predictions for the ?b and Bc mass
3
Theoretical Tools
Effective theories for quarkonium (II)
  • 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.
  • gt Introducing an anisotropy (with a
    temporal lattice of smaller spacing)
  • gt 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
  • gt Fast supercomputers and improved
    staggered fermions
  • gt In the case of quarkonia finite
    mass effects are milder than in B and D mesons
  • Lattice determinations of QCD parameters
  • gt 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.
gt 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
4
cc Sector
Spectroscopy

Foreseen (or confirmed?) observation of the hc
(1P1) state (prior evidence from pp?hc?J/yp is
weak) through the decay chain y?hcp0?hcp0g
by E835 and CLEO-c. Physical interest gt
Comparison with the 13PJ cog test of the
Lorentz nature of the confining potencial,
(e.g. through its spin-spin part) gt 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 gt 13D3,13D2,11D2
states close to the y(3770) mass, quite narrow
and with prominent transitions to
lower c-cbar states. Future possibilities gt
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 gt
Confirming evidence at Tevatron of the X(3872)
discovered by BELLE via the decay mode
X(3872) ? J/? pp- has shown the CDF and D0
discovery potential for new charmonium states
gt 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. gt The observation of double
charm opens up unique perspectives to study charm
spectroscopy (e.g. doubly charmed
baryons) and production and decay dynamics


5
cc Sector
Radiative and exclusive decays (I)

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! gt CLEO-c has
accumulated 1.5 million ?(2S)s allowing to study
the single photon spectrum and determine
BR?(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
gt 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/? into ?, ? and ?c states
can test the underlying dynamics gt assumed to
be dominated by the gluonic contribution gt of
particular interest radiative quarkonium decays
into scalar mesons instead of pseudoscalars
(they might even be glueballs with admixtures of
light quarks)
6
cc Sector
Radiative and exclusive decays (II)

Exclusive decays constitute an interesting
laboratory for investigating corrections to
the leading-twist approach. A systematic study of
such is lacking. For example, gt hadronic
helicity conservation is violated in J/??VP
decays gt longitudinally polarized vector
mesons are forbidden in h c?VV decays gt
leading-twist forbidden cc? BB decays have
sizeable BFs (diquark model?) One important
question to be answered is whether factorization
holds to higher-twist order, taking into account
gt higher- Fock state contributions gt soft
power corrections Especially interesting is the
so-called ?-? puzzle in J/? and ? decays gt
Intrinsic charm component? One of the most
dramatic unsolved problems gt Other points
radiative decays into light hadrons, e.g. J/???p0

Recently, an enhancement near twice the proton
mass was found by BES in the invariant mass
spectrum of the J/? decay into a
proton-antiproton pair, providing evidence for
a bound state (not yet clear if a S- or a P-wave
state). gt result close to the findings in pd
and pp reactions and the BELLE observations in B
decays gt Puzzling is however that no peak is
seen in J/???pp. Suggestions by Rosner

7
bb Sector
Spectroscopy
  • So far no singlet state in the bottomonium family
    has been observed
  • gt hb(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) pp, followed by hb ??b
    ? which is useful to observed the hb state too
  • gt Another good chance to detect hbs is given
    to hadron colliders (through OZI suppressed final
    states like J/? J/?, easy to identify through
    its muonic decay)
  • - at present Tevatron run
  • - with the next generation of B
    experiments, namely BTeV and LHC-b
  • gt 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.
8
bb Sector
and decays
Hadronic transitions can be useful to complete
our picture of heavy quark spectroscopy gt
HTs 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 HTs one can use chiral
symmetry for light mesons and heavy quark spin
symmetry for the heavy states. gt 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 gt 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 gt as the
soft photon would be undetected, this
contribution would unwittingly ascribed to
the tauonic mode, thereby breaking lepton
universality signal of new physics gt Possible
spectroscopic consequences - ?b
width larger than expected -
m?-m?b (hyperfine) splitting larger than expected
9
t t Sector
Top quark pair production at threshold has many
problems remaining to be solved gt NNLL
corrections (RG improved) corrections to the top
pair production current gt complete fixed
order (NNNLO) prediction of the total cross
section gt conceptual issue consistent
treatment of EW corrections including instability
of the top quark and interferences with
non-resonant final states gt 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 ee- Linear
Collider will be in operation. gt realistic
simulations require the treatment of differential
distributions, width and rscattering
effects as well as detector and beam effects
10
Precise measurements
Quark mass and as
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, gt 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 gt 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) gt 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. gt
renormalization group improved calculations could
be applied (already for the top quark) gt
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. gt using the ratio Rm of
the total hadronic decay and leptonic decay
widths gt using lattice QCD
11
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.
  • gt 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) gt Measurements
of the Bc lifetime should give information on the
c- and b-quark mass gt Semi-leptonic decays can
test the spin symmetry of NRQCD and HQET gt Also
interesting the (destructive) interference of the
b?ccs transition and the initial c-quark gt
Study of CP-violation in order to extract the
angle ? in Bc decays
12
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 gt JPC 1- state M(?g) 4 GeV ,
lying in the vicinity of DD threshold
tantalizing possibility of a relatively
narrow state if below!
Charmonium hybrids can be produced and detected
in B decays gt B ? ?g X, BFB ? ?g(all
JPC)X 1 if M lt 4.7 GeV
There are three important decay modes for
charmonium hybrids gt Decays to D(,)
D(,) the challenge is to identify decay modes
which can be exp reconstructed gt Decays to
(ccbar)(light hadrons) the cleanest signature
if the BF is large enough, e.g.
?g
? (?, ?)(light hadrons) Kuang-Yan
mechanism
Also radiative decays may
be relevant, e.g.
?g ? (J/?,hc)?
E1 transition gt Decays to light hadrons
Offer the possibility of producing light exotic
mesons
13
In Media
Relativistic heavy ion program
  • 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.
  • gt 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
  • gt 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
  • gt Lattice QCD at zero temperature
  • - What are the matrix elements of gluon
    and quark operators related to quarkonium
    dissociation ?

14
Experimental facilities and projects
First man-made accelerator (used by Galileo)
Charm factories
CLEO-c will collect high statistics running on
the charmonium JPC1-- resonances. Already data
taking on the y(3686) allowing the following
possibilities (3fb-1) gt Hadronic decays
search for the hc in y??0hc and also for y???
(small BF) gt Detailed studies of cc1, cc2,
cc3 measurement of BFs gt Radiative decays
BFs of y???c y y???c gt 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???J/y or the
double cascade decay y??cc1,c2???J/y???ll-.
gt 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 gt Search for
gluonic excitations through the radiative decay
J/y?gX gt Prospects of making use of y???J/y
to tag J/y(3097), studying its final state
polarization
15
Experimental facilities and projects
Charm factories
  • 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.
  • gt 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/? to ?(3770). For example,
  • gt D and Ds decays will allow the determination
    of CKM matrix elements with a few precision
  • gt A number of important physics topics in the
    t-charm region
  • gt Precise measurement of R, to determine the
    charm mass with very small systematic
    uncertainty
  • gt Search for new physics in charmonium and
    bottomonium decays
  • - Possible lepton number (flavor)
    violation e.g. in J/?? l l decays
  • - CP test with J/? decays (e.g. J/? ? ?
    ?) probing the chromo-electric and magnetic
  • moments of charm quarks

BEPC will be upgraded to become a double-ring
collider
16
Experimental facilities and projects
B factories
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 51035 cm-2s-1 luminosity (a factor 50
of improvement!) along with the BELLE detector.
gt 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 gt hc and
D-wave states 13D3, 13D2 and 11D2 gt
charmonium hybrid states gt 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
17
Experimental facilities and projects
Hadron colliders
Tevatron. High-luminosity Run II is in progress.
The recorded and future large statistics will be
used for gt 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/?, ?(2S),, e.g.
double J/? production or in association
with ccbar gt Decay Studies -
X(3872) ? J/?pp- decay MEs dependence on the
pp invariant mass - hadron decays into
charmonia, e.g. exclusive B decays into final
states involving J/? - Bc studies (mass
and lifetime)
18
Experimental facilities and projects
Hadron colliders
  • 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
  • gt high luminosity with peaks of 2 x 1032
    cm-2s-1 (using stochastic cooling)
  • gt 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 , p, K and p.
  • An intensive spectroscopy program improving
    considerably the statistics
  • will be carried out.
  • gt Ground state of charmonium and its radial
    excitation
  • gt hc resonance of charmonium
  • gt charmonium hybrids
  • gt charmonium in nuclei
  • gt charmonium above open charm threshold
  • . Unlike ee- colliders at GSI all quantum
    numbers are directly accessible.

19
Experimental facilities and projects
Hadron colliders
  • 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 L2x1033cm-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)
  • gt 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/? or ? via their muonic decay
    mode.
  • Study of HQ hadroproduction. One of the first
    measurements at the LHC will be
  • the direct J/? and ? production cross sections
  • gt Extraction of NRQCD matrix elements
  • gt Test of NRQCD factorization polarization of
    J/? and ? resonances at large pT

Bc studies. Large production rates will allow
for precision measurements of Bc properties gt
lifetime, mass
20
Experimental facilities and projects
Hadron colliders
  • 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.
  • gt precision studies of CP
  • gt rare decays of B-mesons
  • gt 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. gt The ?(1S) is expected to
dissolve above the critical temperature -
the spectroscopy of the ? family at LHC energies
should reveal unique information on QGP gt
Significant differences wrt lower energies
(leading to enhancement rather then suppression)
- charmonia produced from bottom decay, D
antiD annihilation and coalescence mechanisms gt
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. gt J/? production suppressed
in heavy-ion collisions wrt proton-nucleus
collisions
21
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
22
In sum, progress in quarkonium physics should
come from the interplay between theory and
experiment from quite different places.
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