Diffraction, Dark Energy, and Higgs Bosons

1
Diffraction, Dark Energy, and Higgs Bosons
Seminar _at_ NESTOR Institute, PYLOS, GREECE, 20 Aug
07
K. Goulianos The Rockefeller University
QCD , Strings, or OTHER?
2
Contents

• Introduction
• Diffraction
• Dark Energy
• Higgs Bosons

3
INTRODUCTION
4
The big bang
5
Blow-hole at Grand Cayman
6
Black Hole Eats Star!
7
What is Dark Energy?

H He
M
E
8
Elementary Particles
9
SU3 Law and Order in the Particle Zoo
D-
Do
D
D
S (1193)
S-
So
S
(1384)
X0(1533)
X-
W-
Isotopic spin I3Q-(BS)/2
Strangeness S
10
QED Quantum Electro-Dynamics
a
m 1.00115965219 ? 0.00000000003
11
The Standard Model
Glashow, Salam, and Weinberg
Higgs field generates Mass !
12
Unification of forces
WEAK 10-14
aW
ne
e-
W-
d
u
charged current
nen -gt pe-
aW
13
Leon Lederman the SM
A good theory should fit on a T-shirt!
AND WHAT ABOUTGRAVITY?
14
String Theory, then?
15
DIFFRACTION
16
p-p Interactions

• Diffractive
• Colorless exchange with
• vacuum quantum numbers

Non-diffractive Color-exchange
rapidity gap
Incident hadrons acquire color and break apart
Incident hadrons retain their quantum
numbers remaining colorless
17
Elastic Scattering
18
Diffraction Dissociation
KG, Phys. Rep. 101, 169 (1983)
Momentum loss fraction
xlt 0.1
Tevatron M ? 0.6 TeV LHC ?
4.4 TeV
19
Diffraction Kinematics
xp
x,t
dN/dh
rapgap
Dh-lnx
h
20
Rapidity Gaps and QCD
21
PHENOMENOLOGY
?
2007
candidates superimposed
22
Diffraction at CDF
sTIm fel (t0)
Elastic scattering
Total cross section
f
f
OPTICAL THEOREM
GAP
h
h
DD
DPE
SDDSDDD
SD
23
CDF Run 1 (1992-1995)
24
CDF forward detectors
25
The MiniPlugs _at_ CDF
26
MiniPlug Construction
About 1500 wavelength shifting fibers of 1 mm
dia. are strung through holes drilled in 36x¼
lead plates sandwiched between reflective Al
sheets and guided into bunches to be viewed
individually by multi-channel photomultipliers.
27
SOFT DIFFRACTION
28
Diffraction and Unitarity

• Unitarity problem
• Using factorization
• and std pomeron flux
• sSD exceeds sT at
• Renormalization
• Normalize Pomeron flux to unity to eliminate
  overlapping gaps

KG, PLB 358 (1995) 379
29
A Scaling Law in Diffraction
KGJM, PRD 59 (1999) 114017
? Independent of S over 6 orders of magnitude in
M2 !
Factorization breaks down so as to ensure
M2-scaling!
30
The QCD Connection
a reflects the size of the emitted cluster,
which is controlled by 1 /as and thereby is
related to e
31
Single Diffraction in QCD
sub-energy x-section
gap probability
Gap probability MUST be normalized to unity!
32
Multigap Diffraction
(KG, hep-ph/0205141)
f
y
33
Multigap Cross Sections
Same suppression as for single gap!
34
Central and Multigap Diffraction

• Double Diffraction Dissociation
• One central gap

• Double Pomeron Exchange
  
• Two forward gaps

• SDD SingleDouble Diffraction
• One forward gap one central gap

Rate for second diffractive gap is not suppressed!
35
Central and Two-Gap Results
36
DARK ENERGY?
37
HARD DIFFRACTION

• Diffractive fractions
• Diffractive structure function
• ? factorization breakdown
• Restoring factorization
• Q2 dependence
• t dependence
• Hard diffraction in QCD

JJ, W, b, J/y
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Hard Diffraction Fractions
Fraction()
Fraction SD/ND ratio at 1800 GeV
All ratios 1 ? uniform suppression
FACTORIZATION !
1.15 (0.55)
W
0.75 (0.10)
JJ
0.62 (0.25)
b
1.45 (0.25)
J/y
39
Diffractive non/Factorization
bmomentum fraction of parton in Pomeron
bxBj/x
The diffractive structure function measured on
the proton side in events with a leading
antiproton is NOT suppressed relative to
predictions based on DDIS
40
Diffractive Structure Function
Systematic uncertainties due to energy scale and
resolution cancel out in the ratio
41
Dijet Properties
SD boosted opposite to pbar
42
ET distributions
43
Diffractive Structure FunctionQ2 dependence
ETjet 100 GeV !

• Small Q2 dependence in region 100 lt Q2 lt 10,000
  GeV2
• Pomeron evolves as the proton!

44
Diffractive Structure Functiont- dependence
Fit ds/dt to a double exponential

• No diffraction dips
• No Q2 dependence in slope
• from inclusive to Q2104 GeV2

• Same slope over entire region of
• 0 lt Q2 lt 4,500 GeV2
• across soft and hard diffraction!

45
Hard Diffraction in QCD
deep sea
valence quarks
Derive diffractive from inclusive PDFs and color
factors
xx
proton
46
HIGGS BOSONS
47
Exclusive dijets and Higgs bosons
Measure exclusive jj gg ? ?
? Calibrate predictions for

H production rates _at_ LHC
Bialas, Landshoff, Phys.Lett. B 256,540
(1991) Khoze, Martin, Ryskin, Eur. Phys. J. C23,
311 (2002) C25,391 (2002)C26,229 (2002) C.
Royon, hep-ph/0308283 B. Cox, A. Pilkington, PRD
72, 094024 (2005) OTHER
KMR sH(LHC) 3 fb S/B 1 if DM 1 GeV
Search for exclusive dijets Measure dijet mass
fraction Look for signal as Rjj? 1
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Exclusive Dijet Signal
b-tagged dijet fraction
Dijet fraction all jets
DIJETS
Exclusive b-jets are suppressed by JZ 0
selection rule
Excess over MC predictions at large dijet mass
fraction
49
RJJ(excl) Data vs MC
Exclusive DPE (DPEMC) ? non-pQCD based on Regge
theory
ExHuME (KMR) gg?gg process ? uses LO pQCD
Shape of excess of events at high Rjj is well
described by both models
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jjexcl Exclusive Dijet Signal
COMPARISON of Inclusive data vs MC _at_ b/c-jet data
vs inclusive
51
JJexcl x-section vs ET(min)
Comparison with hadron level predictions ExHuME
(red) Exclusive DPE in DPEMC (blue)
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JJexcl cross section predictions

• ExHuME Hadron-Level Differential Exclusive Dijet
  Cross Section vs Dijet Mass
• (dotted/red) Default ExHuME prediction
• (points) Derived from CDF Run II Preliminary
  excl. dijet cross sections

Statistical and systematic errors are
propagated from measured cross section
uncertainties using ExHuME Mjj
distribution shapes.
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Looking forward _at_ LHC
TOTEM/CMS ATLAS

• FP420 project http//www.fp420.com/
• Measure protons at 420 m from the IP during
  normal high luminosity running to be used in
  conjunction with CMS and ATLAS
• Feasibility study and RD for Roman Pot detector
  development
• Physics aim pp ? p X p (Higgs, New physics,
  QCD studies)
• Status Project funded by the UK

54
Summary
dark energy?

• CDF - what we have learnt
• M2 scaling ? ds/M2 not a function of s
• multigap diffraction ?restoration of
  factorization!
• flavor independence of diffractive fractions
• small Q2 dependence of SD/ND xBJ-distributions
• t-distributions independent of Q2
• exclusive dijet cross sections favor
  the perturbative QCD over the DPE approach
• LHC - what to do
• Elastic and total cross sections r-value
• High mass (?4 TeV) and multi-gap diffraction
• Exclusive production (FP420 project)