DIFFRACTIVE PHYSICS IN THE NEAR FUTURE

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DIFFRACTIVE PHYSICS IN THE NEAR FUTURE
G. Alves CBPF/RIO
Adriatic 2001 8th ADRIATIC MEETING PARTICLE
PHYSICS IN THE NEW MILLENNIUM
Dubrovnik, Croatia, 4 - 14 September 2001
Outline I - Introduction / Motivation II -
Run II at Tevatron- CDF and Df For
Diffractive Physics III - Conclusion
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I - Introduction / Motivation
Generalities

a
a
aj
b
b
QCD - the theory of Strong Interactions needs
diffraction - 40 of total Cross Section
due to the diffractive evts. - Unified
picture ! Soft and Hard interactions This
correspond to understand the Soft and Hard
Pomeron! - A hadron ? A Glueball? Or
something else? - Does it have a real
partonic structure? - universality same
in e p and ? Same with (hard)
without (soft) jet production? - Is the
Pomeron a representation of different aspects of
the same physics?
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I - Introduction / Motivation
Diffraction one of the oldest subject of physics
still poorly known in Particle Physics
Historical Remarks

• The Diffraction Phenomena was first observed by
• Leonardo Da Vinci (1452-1519) (Principles of
  Optics Electromagnetic
• Theory of Light Max Born and Emil Wolf
  Pergamon Press 1975 USA)

• Leonardo 1452 - 1519
• Grimaldi 1618 - 1665

• Fresnel-Huygens proposed

Each point of a wave edge is a source of
spherical waves.
Good Walker
Diffraction Dissociation of Beam Particles
-Phys.Rev.120,1857(1960)
The characteristics of a Diffractive Process is
I - weak energy dependence II -
strong t dependence III - vacuum quantum
numbers exchange
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Soft Diffraction

• Well described by Regge Model

1. Periferism and Vacuum Quantum Number
Exchange 2. Unitarity 3. Analyticity 4.
Crossing 5. Asymptotic Behavior 6. Agreement with
data
(Froissart-Martin Bound
A very known example is the successfully
parameterized Elastic Scattering by Regge Model
I - weak energy dependence II -
strong t dependence III - vacuum quantum
numbers exchange
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Hard Diffraction

• Hard Diffraction Diffraction Jets

Usual Kinematics
Pomeron Transfer Momentum
Pomeron Momentum Fraction
where Xp is the Scattered Proton Momentum
Fraction
Diffractive Mass
Rapidity Gap
Rapidity
Pomeron Exchange
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Theoretically Ingelman Schlein started a new
view of the Hard Diffraction proposing a Model
G.Ingelman and P.E.Schlein - P.L.152B,256(1985)
Jet Structure in High Mass Diffractive
scattering

• 2 Jets of high pt J1, J2
• 1 Jet spectator opposed to J1 J2
• A quasi elastic system.

The processes can be described by two parts i)
a Pomeron emitted by the antiproton ii) an
interaction between the Pomeron and p the at
high pt
iii) cross sections are given by
s
s



R
d
YP
P
X
d
Y
X
(
)
(
)

f
x
t
(
,
)
R
R
/
p
dx
dtdx
dx
dx
dx
1
2
4
3
4
p
1
2
1
2
1
2
4
4
3
4
4
PomeronFlux
or
obability of
Particle pomeron
Pr
emitting a P
omeron
Y g, e, m, n, p, p, p, n, n
hard scattering
from the proton
Differential Cross
Section
.
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The cross sections are given by
xi is the fraction of the parton momentum pi of
the particle y.

• With the flux given by

where
is the SD cross section
the Pomeron-p total cross section
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Summarizing

• Soft Pomeron can be viewed as the Regge
  trajectory (hadronic
• resonance) saturating the Froissart Bound
  (intercept ? 1.08)

• If we accept that the Pomeron is constituted
  dominantly by
• Gluon and that QCD can have hadrons called
  Glueballs, then,
• it is reasonable to assume that Pomeron and
  Glueballs are
• the same object.

• Hard Processes needs additional contribution to
  the soft ones
• (data on F2, F2C, J/? indicate a trajectory
  with intercept ? 1.4)

A.Donnachie and P.V.Landshoff, hep-ph/0105088
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DIFFRACTIVE PHYSICS TOPICS
A list of the possible subjects to be studied -
our main motivation -
1. Low and High t Elastic Scattering
2. Total Cross Section
3. Inclusive Single Diffraction
4. Inclusive Double Pomeron
5. Hard Double Pomeron Exchange
6. Diffractive Jet Production
7. Diffractive W/Z Boson Production
8. Diffractive Heavy Flavor Production
9. Pomeron Structure Function
10. Correlation (h, angles, t, Mx, b, x, x, ET,
q, ...)
11. Glueballs, Centauros, Higgs
New ideas/topics are welcome!
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1. Low and High t Elastic Scattering

• Even knowing that our priority is Hard
  Diffraction, and that
• Elastic Scattering is well known, it is still
  important to have
• new measurements at the Tevatron energies.

With FPD we have this possibility with a
good accuracy.

• precise selastic ? good extrapolation of
• allowing the use of the Optical Theorem ?
  sTotal
• calibration

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2. Total Cross Section

• At Tevatron we have two experiments giving
  different results for stotal CDF ( 80. mb) and
  E710(73. mb)

• It is important in this case to have a referee
  measurement
• because
• - They are not compatible
• - Unitarity can be violated and
• Froissard Bound can also
• have too early violation.

• It is important to clarify the
• situation a bit uncomfortable
• for models and theories.

Lepton Photon 01-Giuseppe Iacobucci Diffractive
Phenomena
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1. Inclusive Single Diffraction

• One advantage of the Tevatron is the
  Diffractive Mass
• produced in the topology of the Inclusive
  Single Diffraction
• (Mx 450 GeV)

• The event and Associated Topology is easily
  identified
• by RP installed close to a central
  detector.

This topology is a laboratory to study several
problems.
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In the Hard Single Diffraction the associated
topology is identified by the final state with
jets.
Hard Single Diffraction
( Gap )
p
By symmetry
Hard Single Diffraction
( Gap )
p
p
p
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4. Inclusive Double Pomeron
The Inclusive Double Pomeron is interesting for
studies of the Diffractive Mass MX
In this case we do not look for specific jets but
all production and we can trigger especial
events like centauros.
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5. Hard Double Pomeron Exchange
Double Hard Pomeron

• The Topology of the Double
• Hard Pomeron Exchange is
• one of the most interesting
• in the Diffractive Physics.

(Gap)
(Gap)
p
p
p

0

• It is a rich environment to develop
• subtopics . This turn the event very
• attractive in the sense that we have
• a unique chance to observe the
• Pomeron-Pomeron interaction.

( Double Gaps, UA1, . )
( UA8 a 630 GeV,HERA -ep )

• Subtopics like Multiple Jets, Higgs, Centauros
  and Glueballs
• may be observed in this topology.

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6. Diffractive Jet Production

• Jets have been studied by QCD
• in several ways.
• For Diffractive Physics was
• fundamental the discovered of
• UA8, producing jets diffractively.
• We want to study single and
• double jet production using the
• new generation of detectors.
• It is important to include studies
• of the parameters which
• characterizing the jets.

p
( Gap )
p
p
p
p
(Gap)
(Gap)
p
p
p
p
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7. Diffractive Production of W Z Bosons
The Run I of Tevatron produced W and Z but with a
poor statistic.
It is important that in Run II we intend to
increase the statistics and have a better
accuracy.
nL0
nL0
ncal
ncal
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8. Diffractive Heavy Flavor Production

• Heavy Flavor Physics has been studied almost
  one hundred per cent
• as a subject of high pt Physics only. The
  main reason for that is the
• missing instrumentation around detectors to
  trigger heavy flavor
• diffractive events

• We can think in 3 type of studies

Charm - Beauty and Top The question is
It is only missing instrumentation ? A.
Kerman G. Van Dalen Phys. Rep. 106,29 (1984)

• Would be interesting if we measure these
  rates,

E.L.Berger, J.C. Collins, D.E.Soper, G.Sterman
-Nucl.Phys. B286,704(1987)
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9. Pomeron Structure Function
As for all particles, it is important to know
the Structure Function of the Pomeron.
In the case of the Tevatron, the Diffractive
Structure Function have to be well known in order
to test the universality of the Diffractive
Structure Function we have to compare with the
HERA results.
The Study of the Structure Function allow us
better understand the Pomeron
Is the Pomeron an object composed only by gluons,
or quarks or a mixture of both and what are the
rate of each one of the components.?
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10. Kinematic Correlation (h, angles (q, f), t,
Mx, b, x, xp, ET,)
The study of the isolated distributions for each
one of the variables it is important to know the
real behavior of the diffractive dynamics.
Nevertheless it is interesting to use the
correlation between the variables to get hint
about the dynamics sometimes hidden in these
correlations at two and three dimensions.
We have two good examples of the study of the
correlations

• The Mass Slope cos q correlation

• The Lego Plot h x f

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11. Glueballs, Centauros, Higgs
Glueballs Glueballs are objects made by gluons
only. This is a direct consequence of the gluon x
gluon interaction. This is one of the oldest
subject of QCD. We never produced Glueballs
without ambiguity.
The family of Glueballs is numerous
. We have to examine in priority the Oddballs.
Let us show a table with Glueballs and Oddballs.
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A. B. Kaidalov and Yu. A. Simonov "Glueball
masses and Pomeron Trajectory in non perturbative
QCD approach C. Morningstar, M. Peardor, Nucl.
Phys. B63A-C, 1022, (1998) Phys. Rev.
D60,034509, (1999) M. Teper, Hep/th981287
It is important for QCD, that predicts the
existence of glueballs. In the Diffractive
sector it is very important to know it. This
object can be a Pomeron.
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Centauros
Centauros never was observed in Particle
Accelerator Experiments.
Centauros were discovered in Cosmic Ray Physics
as an event with interesting characteristics.
High Multiplicity Hadrons produced with a very
low activity electromagnetic or no
For example a multiplicity of 100 of hadrons and
no
a) F. Halzen - Felix home Page. b) Brazil-Japan
Collab. -Proceed. Of the 21st. Int. Conf.-
Adelaide/ Australia-vol.8,259,1990 c) idem
idem, Prog. Theo.Phys.Suppl. 47,1,1971 d)
C.M.G.Lattes, Y.Fujimoto and S. Hasegawa,
Phys.Rep. 65,151 (1980) e) C.E.Navia et al.
Phys. Rev. D40,2898 (1989) f) C.M.G. Lattes et
all. Phys.Rep.,65,151,(1980)
Some Centauros
Event/Type M(GeV/c2) lt pT
gt(GeV/c) Nh
Centauro 200 - 300 1
- 2 100
Mini-Centauro 20 - 30 1
- 2 15 - 20
Chiron 200
7 - 10 20
Geminion 15 - 30
7 - 10 2
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Higgs
Higgs is a priority for the Run II like was Top
for Run I
Many estimates predict the observability at
Tevatron and some chance of seeing it in
Diffractive events.
The main topology would be the Double Pomeron
Exchange
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Now we have lots of other motivations
Interest in Hard Diffraction grow
CERN/UA8 Discovery of the Hard
Diffraction HERA (H1, ZEUS) - Large Gaps
shows a quark component and F2D shows a
Pomeron dominantly gluonic TEVATRON (CDF,
) - Jets and diffractive W production.
Results at 1800 and 630 GeV( ) Great
progress Theoretical and Phenomenological
approaches
1974 C
1977 B
1995 T
1993 UA8
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• Some processes well-known, need more accurately
  measurements
• ( Ex. Diffractive Dijet.)
• Some processes have new results from CDFDØ,
  but no double
• tagged track events yet. (hard double
  pomeron)
• Data Samples are statistically limited, lack
  information
• on t ( and at Tevatron x ) dependence.
• New possibilities ? centauros, glueballs,
  Higgs

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Far Future
LHC (14 TeV) Plans for using Roman
Pots for Diffractive physics at CMS.
Atlas, Alice also have plans for diffraction.
Results of the TEVATRON will be important for
LHC -Diffractive Physics.

• Let us show now how we can do use of the
  Rapidity Gap technique to identify
• good diffractive topology events.

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Color-Singlet Signature Rapidity Gaps
Large Rapidity Gap ---gtgt a good signature of
Diffractive Events
Color Exchange
Inclusive Multiplicity
Color-Singlet
N
N
N

(no particles)

n
n
n
0
Particle Detection Inefficiency
Fragmentation Spectator Interactions
Detector Noise
Decreased S/B
N
(Observable Signal)
N
N
(some particles)

(observed signal)

n
n
ngt0
n
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EVENT TOPOLOGIES
Soft Processes
Hard Processes (jet production)
p
Hard Double Pomeron
( Double Gaps, UA1, CDF,DO . )
Let us show CDF and DØ prospects
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• To have a real idea about diffraction we have
  to measure
• events which will reveal the nature of the
  Pomeron.

• We need to build appropriated triggers,
  instrumentation
• with the capability to detect both the
  scattered
• particles and jets/fragments on a central
  detector
• (Calorimeters)
  Dzero/Fermilab.

Diffraction
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II - Run II-Tevatron CDF and Df (FPD)
CDF PROSPECTS
The upgrade for CDF in view of the Diffractive
Physics, are
1. Improve dipole spectrometer (R.Pots).
(Accumulate more luminosity - pots added at
the end of Run I)

• Use the miniplug for triggering
• Diffractive events.

• Add new scintillating counters at
• large rapidity.

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Interaction Point
Each Miniplug has -50 lead plates of 1/4 thick
corresponding to a total of 2 interactions
lengths and 60 radiation length. -288 signal
towers viewed by 18 MCPMTs (16 channels
each) -Total weight is 0.8 tons. (one miniplug)
The Scintillating Fiber Cells
Front view for a Miniplug showing the proposed
segmentation
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For DØ
The Tevatron itself was submitted to many
upgrades RUN II
NEW TEVATRON
Luminosity
L 2 x 1032 cm-2 s-1
( 36 bunches )
Energy
120 GeV
8 GeV
400 MeV
750 KeV
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D0 Detector

• Solenoidal magnet Preshowers
• Tracking, Fibers, Silicon Front End Elect.,
  DAQ
• Forward Muons

New for Run II
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18 Roman Pots giving 9 independent spectrometers
The Combination of the Quadrupoles Dipoles
gives the possibility 1. Proton and
Antiproton Detection a) Double Pomeron (
Unique! ) b) elastic for alignment,
calibration, Luminosity and Monitoring
c) halo rejection 2. Low and high t
acceptance 3. Background
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D0 Detector h - Phase Space
-4.5 Cal. Hadronic 4.5
-3.7 Cal. Electr. 3.7
-3. SMT 3.
-1.7 Scin.Fib.1.7
-4.4 Luminosity Mon. 4.4
-7 Roman Pots - FPD -
7
-8 -6 -4 -2 h 0
2 4 6 8
Central Fiber Tracker -1.7 lt h lt
1.7 Central PreShower -1.3 lt h lt
1.3 Forward PreShower 1.4 lt h lt
2.5 CALorimeter -4.5 lt h
lt 4.5 MUON
-2.0 lt h lt 2.0
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ACCEPTANCE
Quadrupole ( )
450 400 350 280 200
x
MX(GeV)
Geometric ( ) Acceptance
GeV2
f
450 400 350 280 200
x
Dipole ( only)
MX(GeV)
GeV2
Dipole acceptance better at low t, large
x Cross section dominated by low t
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Acceptance x Pot Position

• Acceptance is a strong function of pot position

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Tevatron Reconfiguration
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Roman Pot Design
50 l/s ion pump
Worm gear assembly
y
x
Pot/Detector
z
Beam
Step motor

• Used 316L Stainless Steel
• Parts are degreased and vacuum degassed
• Goal to achieve 10-11 Torr
• Will use Fermilab Style Controls
• Bakeout castle, then insert fiber detectors

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Roman Pot Arm Assembly
Detector Inserted into cylinder until it reaches
thin window
Threaded Cylinder
Step Motor
Bellows
Flange Connecting to Vaccum Vessel
Thin Window and Flange assembly
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NIKHEF Window and Castle Stand

• Used finite element analysis to model different
  window options
• Built three types of pots and studied deflection
  with pressurized helium.
• 150 micron foil with
• elliptical cutout gives
• excellent results

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Position on the Beam Line
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• 6 layers per detector in 3 planes and a trigger
  scintillator
• U and V at 45 degrees to X, 90 degrees to each
  other
• U and V planes have 20 fibers/ layer, X plane
  have 16 fibers
• () layers in a plane offset by 2/3 fiber -gt
  80?m resolution
• Each channel filled with four fibers
• 2 detectors in a spectrometer

17.39 mm
V
V
Trigger
X
X
U
U
17.39 mm
1 mm
0.8 mm
3.2 mm
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The total Detector Frame Assembled Prototype
Set up of tests
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RUN II EVENT DISPLAYS
HARD DIFFRACTIVE CANDIDATE
HARD DOUBLE POMERON CANDIDATE
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D0/FPD Expected
To work in these topics we need to build our
future sample
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III - Conclusion
QCD needs diffraction - Interest in the
field had been growing steadily

• CDF and built new detectors improving
• the future Diffractive physics at Tevatron.
• CDF is upgrading its already existing dipole
• spectrometer and adding a Miniplug
  Calorimeter.

• FPD will be a completely integrated
  sub-detector of
• which will maximize Run II physics
  potential
• Help to understand Hard diffraction, with large
  data samples
• and more precise measurements
• Expected for (1 fb-1)
• 1 K Diffractive W
• 3 K Hard Double Pomeron
• 500 K Diffractive Dijets