Transcript Slide 1
DIFFRACTION and Forward Physics–2
M. Arneodo, M.Diehl, V.A.Khoze, P.Newman &
1. New theoretical results presented at the 4th Workshop
2. Selected hot topics:
survival of the survival factor,
basic soft cross-sections at the LHC
3. What can HERA still provide ?
4. Selected early LHC measurements to test predictions
for diffractive processes
Apologies to those excellent & enthusiastic speakers,
whose results were not (properly) covered
(lack of time or / and expertise)
Selection: -as seen through the eyes of the needs of Forward Physics Community
-minimal overlap with other WGs
some overlap : SATURATION
JB – nontrivial task of transferring a theoretical description of saturation from HERA to the LHC
K. G-B, GW –sensitivity of the Diffractive DIS to the saturation
sat. effects quantified- GW
Exclusive Central Production
Very promising addition to the
‘party line’ Higgs studies at the LHC
and even at the ILC/CLIC
(KMR, J.Ellis et al, Manchester group )
•Selection rules mean that central system is
0++ pinning down the quantum numbers
• CP violation in the Higgs sector shows up
directly as azimuthal asymmetries
• Tagging the protons means excellent mass
resolution (~ GeV) irrespective of the decay
products of the central system. LO QCD
•Proton tagging may be the discovery
channel in certain regions of the MSSM.
• Unique access to a host of interesting
Very schematically: exclusive central production is a glue – glue collider where
you know the beam energy of the gluons - source of pure gluon jets - and central
production of any 0++ state which couples strongly to glue is a possibility …
(P. Bussey, C. Royon)
Improved during this
(already a bit outdated)
Photon-photon and photon-proton collider @ LHC
(P. Bussey, J. Nystrand,M. Strikman)
, ee QED processes
WW anomalous couplings
squark, top… pairs
LHC as a High Energy Collider
(P. Bussey )
Cross sections for
various γγ processes.
The dimuon process
may be good for LHC
W+W- has a large cross section
of 100 fb.
Recently -renewal of the interest
Exclusive Channels in pp -collisions
G. Watt, L.Motyka, A.Martin, J.Nystrand
in a peaceful coexistence
exclusive J/ from HERA data as an independent source of information on unintegr. gluons,
needed for the H-Central Excl. Higgs Production (TT,GW)
(GW, LM, JN)
Exclusive production at the LHC as probe of unintegrated gluons
Give us unintegrated gluons in advance (P.Bussey )
a nice way to search for the Odderon ( LM, AM, JN)
a potential discovery channel
(L. Motyka, A.Martin)
(R. Schicker, , J/ - RG)
G. Watt, L.Motyka
(good agreement with J.Nystrand
and KMR )
Selected Hot Topics
Importance for the Forward Physics Studies at the LHC
Serve as a litmus paper indicator of the level of our knowledge
(theory & experiment) on diffractive physics at high energies
Survival of the Survival Factor
(Regular talks by U. Maor (GLM), A. Martin (KMR) and M. Strikman (FHSW))
Account for the absorption effects -necessitated by unitarity
S² -a crucial ingredient of the calculations of the rate of the Central Excl. Diffractive
Prospects of New Physics studies in the Forward Proton mode
qualitatively new stage –a ‘delivery’ of our meetings
• orders of magnitude differences in theoretical expectations – are a history
(not so long ago-
between Scylla and Charybdis)
new (encouraging) CED Tevatron results available, more results to come (K. Goulianos, J. Pinfold)
• we are discussing now the differences on the level of a factor of (4-5)
(K . Goulianos)
PRD to appear soon
A killing blow to the wide range of theoretical models.
PT LO undisputable
(a factor of 4-5 diff. )
weak (~1/2) suppression
it might be much worse
Approach to the Black Disc Regime
(how rapid is it above 2 TeV ?)
START: at 2 TeV
slow (logarithmic) rise
2. FHSW BDR for energies 2 TeV
by few % at the LHC
(soft interactions and hard dipole-proton int. up to
3. GLM(M) two components : ‘conservative’ + BDR-like
(tot) , (el) , (SD)
Bread and butter of TOTEM and ALFA measurements
Importance for various LHC studies ( e.g. notorious Pile-Up)
Low mass SD (DD)- one of the major current limitations on the models
( still not sufficient exp. Information)
KMR-07, A. Martin: relatively low (about 20% below the ‘standard’ central value) value of (tot) at the LHC
( S.Sapeta and K. Golec-Biernat-05)
(tot) 90 mb
…cosmic rays, (early) LHC tests – coming soon
inescapable consequence of the absorptive corrections caused by the higher-mass excitations (A.Martin)
GLM (arXiv; 0805.0418): (tot ) =110.5 mb,
(el) =25.3 mb
(GLM)M (arXiv; 0805.2799): (tot ) = 92,1 mb,
(el) =20.9 mb
(tot ) =90.5 mb, (el) =20.8 mb
GLM(M)- essential improvement of their description of the Tevatron elastic and SD data
Selection Criteria for the Models of Soft Diffraction
We have to be open-eyed when the soft physics is involved.
Theoretical models contain various assumptions and parameters.
Available data on soft diffraction at high energies are still fragmentary,
especially concerning the (low mass) diffractive dissociation.
A viable model should:
incorporate the inelastic diffraction :SD, DD
(for instance 2-3 channel eikonal of KMR or GLM(M))
describe all the existing experimental data on elastic scattering and SD ,DD and CED
at the Tevatron energies and below (A. Martin; GLM(M), 0805.2799 )
be able to explain the existing CDF data on the HERA-Tevatron factorization breaking
and on the CED production of the di-jets, di-photons, , J/, .., lead. neutr. at HERA
provide testable pre-dictions or at least post-dictions for the Tevatron and HERA
So far KMR model has passed these tests.
Only a large enough data set would impose the restriction order on the theoretical models and to create a
full confidence in the determination of S².
Program of Early LHC measurements (KMR, A. Martin)
LET THE DATA TALK !
What can HERA still provide ?
test higher twists
t- depencences (VM, (V)FPS)
More detailed data on proton dissociation in diffractive J/ production
(better statistics, M²-slicing).
Improved statistics on exclusive - production (not sufficient at the moment).
The ratio of diffractive to exclusive dijets, photo to electroproduction.
Transverse momentum distribution of secondaries in the ‘Pomeron fragmentation’.
The Extraction of the Bare Triple-Pomeron Vertex
-a crucial ingredient for
understanding diffraction (e.g. S² calc.)
A way to extract the information on
Existing (ZEUS) data on J/ -still fragmentary
Needed: - improved statistics;
-distributions over M²Y
-inelast. diffractive data;
small size- component
(small rescatter. effects)
p J / () Y
(by integration over ZEUS M Y range)
(after acconting for the second. traject.) (A. Martin)
Importance of an explicit measurement of the Y-system mass spectrum.
To perform a full triple-Regge analysis with different contributions quantified.
Are the early LHC runs,
without proton taggers,
able to check estimates
for pp p+A+p ?
Possible checks of:
(i) survival factor S2:
(ii) generalised gluon fg :
(iii) Sudakov factor T :
(iv) soft-hard factorisation
(enhanced absorptive corrn)
3 central jets
#(inclusive A) evts
with A = W, dijet, …
High sensitivity to the
parameters of models for
LHC with 220m and 420m Forward Taggers
y=-ln , =(1-x)
TOTEM, ALFA, ALICE (RG) ?
S2 ~ 0.02
Exposing the contribution of the Perturbative Pomeron to DDIS
(G. Watt, A.Martin and M. Ryskin (2006))
The perturbative .resolved Pomeron contribution.
Nonperturbative resolved Pomeron.
Measurements of the kt of secondaries in the ‘Pomeron fragmentation’ (edge of LRG).
The kt distribution of the lowest jet should obey the power law – in marked contrast
with the expectations based on Regge-factorization.
Larger kt of the secondaries with the long power-like tail should be observed.
Very promising addition to the ‘party line’ Higgs studies at the LHC
and even at the ILC/CLIC
(KMR, J.Ellis et al, Manchester )
Improved during this
coming (very) soon