Transcript Evidences on Pionization Contributions to Hard Parton

Evidences on Pionization Contributions to
Hard Parton Energy Loss at A-A Collision
-- heavy quark ebergy loss & jets
1. Recent STAR preliminary jet results in A-A (“paradox”)
2. Recalling the induced coherent radiation physical picture, jet
develop. (AO), heavy vs light quark
3. The space-time picture for jet creation & EL---- the effective
jet-QGM collision
4.Theory of Pionization and Extended Eikonal Formula, and its
consequent physical picture on high energy collision (the
stochastic aspect)
5. Discus.
Quests on factorization and hints for further
investigation theo. /exp.
Recent Preliminary jet results in A-A from STAR
What is a jet?
sometimes one talking about factorization, on-shell/pinch
trivial from uncertainty relation: one parton can be factorized into initial/final state should live long!
Jet is what mimics the final state hard parton, dressed by collinear radiations
originated from ‘very hard' paron, t~1/Q; subsequently
dressed/developing via ''parton shower"('DGLAP');
cone protected/reserved by 'angular ordering';
----collinear: a tech. or a fact? (naive: denominator of
propagator determing probab.; will been seen again
and again );
-----coherent: many particles
jet algorithm, dated back to Sterman & Weinberg,
infrared safe, partonic and hadronic levels
exp. facts
One of the first observed 3-jets by TASSO at PETRA as evidence for gluon existence
vs:
The A-A final states
plb86,243
cone,
KT,
JADE,
S-W
...see, eg, G. P. Salam
http://www.lpthe.jussieu.fr/~salam/
Recent Preliminary jet results in A-A from STAR
?
(0809.1609)
The key point may be background subtraction
Possible Questions
• It is said that there is geometric bias for
inclusive spectrum (and/or di-hadron
correlation?), but
• Only the highest energy jet per event is selected
as the reconstructed jet----Does this an apparent
bias?
• Is the K_T algorithm more reliable in
reconstructing the jet which includes all the
collinear radiation?
• Can we use JADE to see differences? see
following
Recent Preliminary jet results in A-A from STAR
(0809.1419)
Recent Preliminary jet results in A-A from STAR
(0809.1419)
?
but quite flat! so at
least a narrow region
independent of the jet
energy under-estimat.
Induced Radiation Physical Picture, key word:
Cohenrence
D,K :plb 519, 199
Induced Radiation Physical Picture
•
•
cohenrent induced radiation considered as dominant contribution.
The puzzle from exp.
Is bremss. dominant mech. for energy loss in gauge
theory at high energies?
• “…If the matter is one that can be settled
by observation, make the observation
yourself. Aristotle could have avoided the
mistake of thinking that women have
fewer teeth than men, by the simple
device of asking Mrs. Aristotle to keep
her mouth open while he counted. He did
not do so because he thought he
knew…”
--How to Avoid Foolish Opinions (Russell, B)
• If Galileo had believed in Aristotle, we
may have no Physics today…
• Let’s see how an muon loses energy by
eyes of ourselves
To uniformly understand all these,
we need a physical picture
• jet creation: 1/p_T
• jet invariant mass M<<p_T, 1/M is the time for the jet to
be 'shaped', jet algorithm insensitive to scale<M
• A composite 'particle' of E(~p_T ) but mass M: large
energy relativistic particle, irrelevant to process
• Immature 'hit' the vacuum or QGM, the different fate after
t~1/M to 1fm or 5fm...
• For A-A the effective collision between jet and QGM,
quite in common with h-h!
• In h-h, the produced particles which take away the
energy of the projectile belong to 1) fireball (fragments)
or 2) pionization...
Fireball--limiting fragmentation
J. Benecke, T.T. Chou, Chen-Ning Yang, E. Yen, PR188,2159
In fragmnetation region, always the same...effectve jet-QGM interaction could be added
Now plareau---theory of pionization (prd3,2195; prl23,1311)
in the days of birth of parton model (prl23,1415/prl23,1311)
• Different region of Physics but leading to parton pic.
also! (Cheng & Wu PK Feynman), on the partonic
process of plateau distribution
• Physically, fireball vs pionization; bremsstrahlung
vs pair production
Extended Eikonal Formula and its Consequences
(Cheng & Wu, Expanding Protons: Scattering at High Energies)
• In high energy interactions, the S-matrix takes the form in
the impact space


S (b , T )  ei (b ,T ) ,
1
T
ln s
2
• This is Operator, the eikonal (operator) representing the
sum of the lowest order amplitudes of all reactions, with the
gluon (Y-M/N-A) propagators replaced by Regge poles
(reggeized)
• the physical meaning/consequences:
Extended Eikonal Formula and its Consequences
• A stochastic picture
Concluding remarks with few
conclusions
• the opportunities of LHC physics
in the hadronic aspects.
Physics opportunities in LHC era
---the strong interaction aspect
LHC Performance Workshop, Chamonix 2009
…… Under a proposal submitted to CERN management, we will have physics data in
late 2009, and there is a strong recommendation to run the LHC through the winter
and on to autumn 2010 until we have substantial quantities of data for the
experiments. With this change to the schedule, our goal for the LHC’s first running
period is an integrated luminosity of more than 200 pb-1 operating at 5 TeV per beam,
sufficient for the first new physics measurements to be made. This, I believe, is the
best possible scenario for the LHC and for particle physics…… --Rolf Heuer (DG)
LHC, a discovery collider, rather than…
But for many purposes, we have to put a hand into the garbage to look for the strong
interactions, which is crucial to understand what state it is after the collision. How far
this investigation will affect the QGP study and furthermore the cosmology?... We
often say generating a little bang, but to what extent…
A not comprehensive history
just seen from CERN
• Before Carlo Rubbia, ISR, PS and SPS (before it
is a ‘collider’) Strong interactions, maybe
including hadronization models/ (several
exceptional in world, J/Psi).
sqrt(s)<~30GeV (sps fixed target,1976)
• To create W+-Z0, when one knows its mass quite
well (dif. from that of Higgs;) before seeing it.
Key: enough energy to create
The jumping by realizing collider
sqrt(s)~>540GeV (sps collider,1981)
Phys. Interest
Totally changed.
Strong inter. Is
Backgroud,
i.e., garbage
We would like
To get rid of., esp. in
The hadron collider.
Now
• The 'Rubbia style' research is still the most popular and proper…
• But we need to understand the collision of 2 protons or Lead atoms as whole, e.g.,
the total cross section, the multi-production, including all the soft, inelasticity.
Here I presented the importance for RHIC.
• There is discussion for exclusive Higgs production, the forward exp. of LHC
• for cosmology, etc. (later) : CGC.
An example: multiplicity-associate
observables
Not to forget: Factorization only valid for inclusive,
and generally proved to one loop
Sigh: EL sig./not?
Let's suppose it!
Diff. phys. pic
• This is the jet development.
Virtuality: Q>>K_t1>>….>K_tc, the pionization
Is of higher orders (at least 2), only possibly
contrib. to the inter-jet behaviours
• For the EL the virtuality keeps on k_t0,
which is quite like pp scattering without
hard jet! Just taking the medium as target.
Here pionization is of the same order as
bremm, and give the platform
Concluding remarks with few
conclusions
• On factorization: We often heard about on-shell/pinch,
which quite trivial from uncertainty relation: one parton can
be factorized into initial/final state should live long! So the
eikonal is very natural thing seen from Cheng & Wu’s t  1
formulae. Jet is who mimics the final state parton, dressedE
by collinear radiations
• Not to forget: Factorization only valid for inclusive, and
generally proved to one loop
• Why would not guys open an eye to muon (QED), in which
the experimentalists teach us: In their estimations as well as
measurements, they have involved the pair production and
have shown that it is as important as bremsstrahlung and
eventually exceeds the latter when energy increases!
• the opportunities of LHC physics in the hadronic aspects.