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1Mike Albrow Diffraction in High Energy Collisions CERN June09
Diffraction in High Energy Collisions
Mike Albrow (Fermilab)
FNAL-CERN School June 2009
2Mike Albrow Diffraction in High Energy Collisions CERN June09
Diffraction in High Energy Collisions(a.k.a Vacuum Exchange, Vacuum Excitation)
Mike Albrow, Fermilab
Landscape: from elastic scattering to p + H + p
Basics: Elastic and Total x-section, diffractive excitation
Double Pomeron Exchange = Vacuum Excitation
Central Exclusive Production at Tevatron
Central Exclusive Production at LHC : etcllWWH ,~~
,,
3Mike Albrow Diffraction in High Energy Collisions CERN June09
From elastic scattering to exclusive Higgs boson production
H
p
ppp
pp
p
p= gluon
But these are related processes! We will get to that.
About 25% of σ(total) About of σ(total)1310
Standard Model: Fundamental matter particles are fermions:Spin ½ leptons and quarks u,d,s,c,b,t
and force particles are bosons: Spin 1 γ, g, W, Z (& spin 0 H)(In principle also Spin 2 graviton, but negligible so far, …)
τμe ντ,,νμ,,νe,
Exchanges Elastic: Q = 0, colour = 0, J >=1 @ H.E.
4Mike Albrow Diffraction in High Energy Collisions CERN June09
In ancient times, pre-QCD (1960’s), Theory of strong interactions being developed: “Regge Theory”Pre-quarks, pre-gluons, pre-deep inelastic scattering.
Based on scattering amplitudes “S”(Square cross sections) S(s,t)S(s,t) required to be:Analytic (no singularities)Unitary (no probabilities > 1)Crossing symmetric (s t)
0
p n
s t
t-channel exchange dominatedby virtual:
)()( 0 pnnp All good things!
This still gives the best description of low-E reactions e.g.
But: Effective angular momentum / spin of exchange α(t) and complex
np 0
QCD became dominant, Regge theory almost left behind.
5Mike Albrow Diffraction in High Energy Collisions CERN June09
Total cross sectionElastic scatteringDiffractive excitation
Much of strong interaction physics is here.Not (yet) described by/understood in QCDWhen Q^2 small α(Q^2) large, “non-perturbative”
COMPETE Collbn fits
LHC
Expect σT ~ 110 nbHow to measure?Total rate inelasticNeed LuminosityElastic scatteringDedicated expt: TOTEM
Strong coupling notRegge spin!
6Mike Albrow Diffraction in High Energy Collisions CERN June09
ijT
i
j=
i
j j
i2
=
dt
d ijel
α(t=0)
α(t)
ii
jj
jj
ii 2
Total cross section and elastic scattering closely related:
Elastic scattering described by amplitude:
Total cross section by Imaginary part of forward scattering amplitude.Regge theory:
2|),(| tsfdt
d ijel
)0,( Im.4)( sfsijT
k
kjikijT
kss ]1)0([)0()0()( ]1)([222
16
)()( t
k
jkikijel ks
tt
dt
d
Optical theorem
Couplings at vertices and propagator (~ Feynman diagrams)
k
k
7Mike Albrow Diffraction in High Energy Collisions CERN June09
Relation between σT and dσ/dt exploited at LHC by TOTEM
CMS
Measure small angle elastic and total rate simultaneously:
Can derive both σT and machine luminosity!Calibrate luminosity monitors. Coulomb scattering: known cross section but extremely hard at LHC.
Another QED process may be better for luminosity calibration: μμγγ (later)
8Mike Albrow Diffraction in High Energy Collisions CERN June09
Total and elastic cross sections: fall then rise (universal)
ln s
RP
R(t), P(t)
R (Reggeon) = sum of all allowed meson exchanges P (Pomeron) = (?) sum of all allowednon-meson (gg etc?) exchanges. Glueballs
qq ρ, ω, ρ etc
( )pp
iα (t=0) -1
-0.45R
+0.08P
Two terms: s
α ( 0) 0.55 s
α ( 0) 1.08 s
t
t
2α(t=0) - 2Total Elastic : ~ s
s t
α(t) effective spin of exchange
9Mike Albrow Diffraction in High Energy Collisions CERN June09
k
kjikijT
kss ]1)0([)0()0()(
If α(0) (~ J) > 1 total and elastic cross sections rise with s < 1 fallAt low energy ρ-exchange dominates, butAt high energy (rising cross sections)another strongly interacting exchange with α(0) > 1 (1+ε) dominates. POMERON IP
5.0~)0(
15.1~)0(IP
)(tIPlongitudinal rapidity y
p p
p
p
Other exchanges with J >= 1:Photon γ and Z (between q, p would break up)
IP
10Mike Albrow Diffraction in High Energy Collisions CERN June09
12 2313
12 23
β + ββ =
1+β βtanh a tanh b
tanh (a+b)1 tanh a tanh b
β
y
12 12So: identify β with tanh y
For small values speedand rapidity y are identical
β
As β 1.0 y
Rapidity
-10rapidity = 0 rapidity ~ 10Rapidity Gap
Relativistic speed addition Hyperbolic tanh addition
z
z
pE
pEy ln
2
1
2tanln)0m(
y
11Mike Albrow Diffraction in High Energy Collisions CERN June09
pp elastic scattering at CERN ISR.Note “diffraction pattern”
Small t, exponential, ~ 1/”size of p”Large t ~ << 1 fermi, structure
VERY small t, γ-exchangeLarge distance ( several fm)Coulomb beats strongCoulomb scattering
Coulomb cross section is ~ known (QED) … so Lumi calibrator
12Mike Albrow Diffraction in High Energy Collisions CERN June09
At LHC large angle elastic scattering uncertain!
Fig. from TOTEM (Latino)
p
p
ggg
0.1 fm
Proton structure intermediate between “point-like” andparton (q+g) beam.If 2 q scattered through “large”angle, 3rd must also orp breaks up.
A handle on IP in q/g terms.
13Mike Albrow Diffraction in High Energy Collisions CERN June09
Rapidity gaps, with (almost) no Regge theory
The mother of all rapidity gaps Δy …. Elastic scattering:
Gap = no particles:
= 24.4 LEP e+e-= 8.4 ISR pp= 15.3 TeV pp= 18.6 LHC pp
epm
s
/beam lny
epm
sy
/
ln.2
t
Rap-gap cross sections go like: yy eey ).1J().1)0(( ~~)( Thus: over large gaps exchange has J >= 1, Q = 0, color singlet.Only 2 possibilities: Photon γ (in ee and pp and ep)
Gluon (ep and pp) … ?color!!? Cancel it with >= 1 other gluon. Call it pomeron (gg) α(0)=1+εPomeron has C = +1 (2 gluons OK). C = -1 OK with (ggg) : odderonZ obeys the above rules, OK in e+e- but p inevitably break up.
14Mike Albrow Diffraction in High Energy Collisions CERN June09
Large ( >~4) rapidity gaps only possible by (t) exchange of 4-momentum with:
No color or charge, and effective spin at t ~ 0 >= 1. J = 1, α(0) >=1. But (a) we have such large gaps in strong interactions (b) QCD is THE theory of strong interactions. Unlike QED, there is no elementary (q,g) object with these properties. (c) In QCD, with Regge theory to describe exchanges of states in the t-channel, only >= 2 g exchange can work.
gg (C = +1) Pomeranchukon Pomeron IPggg (C = -1) Odderon O(not yet detected. α < 1 ?)
Isaak Pomeranchuk1913 - 1966Tullio Regge
15Mike Albrow Diffraction in High Energy Collisions CERN June09
)/(.
12
2
sMddt
df
Single Diffractive Dissociation : at low energies ...,, Knpp
At ISR energies 7.4 22-63 GeV found scaling high x_F peak.Diffractive excitation of high mass “states”
s
sM
sMxs
M
p
pxx
F
Beam
zFeynmanF
22.0~
05.0~)1(
95.0~
max
max
2
)( Fxp
Mts
16Mike Albrow Diffraction in High Energy Collisions CERN June09
PS 7.4 --- 1.6 resonancesISR 63 --- 14Tevatron 1960 --- 430 Jets/W/ZLHC1 10,000 --- 2200 top ??
Diffractive excitation range (“rule of thumb”) sM 22.0~max
smaxM
(GeV)
p
IP
p
p-IP total cross sectionoptical theorem :p-IP elastic scattering
IP .. at high MIPIP
2
ln2 (ln 3)
3
2
ln ln 3
20
1 0.05
X
ss
X
XF
M s
e sM e
e
Mx
s
17Mike Albrow Diffraction in High Energy Collisions CERN June09
Ingelman-Schlein description of high mass diffractionSDE = Single Diffractive Excitation
Suppose IP has constituent (q,g) structure F(Q2,β=x)Go into frame of X, and look for jets. Kinematics tells parton momentum fractions β.
Jets in SDE observed at CERN SppS Collider (not v. high ET)ET > 20 GeV jets in CDF, D0 at Tevatron.
X
J
J
p IP
( )1 J JBj T
jets
x E es
PARTONBj
PROTON
px
p
18Mike Albrow Diffraction in High Energy Collisions CERN June09
Diffractive Di-Jets and Diffractive Structure Functions
pSeen in
Roman Pots
1xp T
particles
E es
( , conservation)zp E
Curves normalized here
At this Luminosity, pile-updominates pJJ trigger.Require(effectively rap-gap on pbar side)
xp p
1 zp
beam
p
p
Excluding p
SDE of hard states, eg t-tbarrequires no pile-up to associatefwd p with t-tbar event.
19Mike Albrow Diffraction in High Energy Collisions CERN June09
Single Diffractive Di-Jets p-JJ cont.
4-vectors
t-distribution ~ independent of
tRatio of diffractive : non-diffractive
structure functions
2 2( ) ( )BEAM OUT Tt p p p p
( )TE J
20Mike Albrow Diffraction in High Energy Collisions CERN June09
HERA (ep) Deep Inelastic Scattering & Diffractive DIS
2 2 22 2F ( , ) ( ) ( , , , )diff
x Q x e q x F x Q t The normal structure function conditional on leading proton (or gap)
Defined independently of notionof the exchange (“pomeron”)Measured in detail by H1 and ZEUS
Interpretable as measuring thestructure of the pomeron
Bjx
JJ
-yT
jets
4F (x) = x{g(x) [q(x)+q(x)]}
91
x = E es
CDF: measured with jets
Rapidity gaps suppressed in ppcompared with ep. Gaps don’t survive additional interactions.
“Rapidity Gap Survival Probability”Bjx
21Mike Albrow Diffraction in High Energy Collisions CERN June09
Diffractive (SDE) production of W & Z (CDF)
About 1% of all W & Z at Tevatron produced diffractively q / qbar in IP at Q^2 ~ M(W)^2
W
p stays intact
0.03 < xi < 0.10|t| < 1 GeV2
22Mike Albrow Diffraction in High Energy Collisions CERN June09
Diffractive production of Z (SDE) at Tevatron
Diffractively produced Z have small pT and y opposite p
23Mike Albrow Diffraction in High Energy Collisions CERN June09
Rapidity Gaps Between Jets : JGJ
y
J J
Predicted by Bjorken.Observed by D0 and CDF in Run 1 (1995)
Charged track multiplicity in central 2.5 – 4.0units of rapidity between jets <ET> ~ 65 GeV.0.85% +/- ~ 0.24% have gaps. [D0 < 1.1% @ 95% CL]
Is high-Q2 q/g scatter by color-singlet?BFKL Pomeron (mostly)?
J
J J
J
...or by single g, with softcolor exchange across event?
GAP
Early study at LHC?
24Mike Albrow Diffraction in High Energy Collisions CERN June09
BFKL and Mueller-Navelet Jets
Color singlet (IP) exchange between quarksEnhancement over 1g exchange – multiRegge gluon ladderJets with large y separation …Δy >~ 5n minijets in between (inelastic case)Large gap in between (elastic case)
TMeasure fn(η, p , s, Δη)Fundamental empirical probe of new regime:non-perturbative QCD at short distances.
S S
Cross section enhanced
4 ln 2α 0.5 for α 0.19
~ ln ~ 3 4
cBFKL
s
t
N
sn
t
q
q
gg
25Mike Albrow Diffraction in High Energy Collisions CERN June09
Central Diffractive Production or Double Pomeron ExchangeRemember:
p p
p p
IP
Double-triple-Reggeor Quintuple Regge:Must happen &rate calculable in RT
IP + IP IP + IP elasticOptical theorem IP + IP X total cross section
p pX
units3~y units3~y(better > 4) rapidity gaps = no hadrons p
2p m
sln2
m
sln
Full range:
At LHC(10) Δy(p-p) = 18.5. 18.5-6=12.5
GeV 520~e~(max)M
5.12GeV)1(~E
Mln2
6.25X
T
X
26Mike Albrow Diffraction in High Energy Collisions CERN June09
Vacuum Excitation (Lab frame)
p
p
p
pp
pp
G
J
J
1)
2)
3A)
3B)
1536 TeV
vacuum vacuum
Soft recoil, no excitation,no forward pion production, ...
all
Vacuum = Physics
27Mike Albrow Diffraction in High Energy Collisions CERN June09
GeV 520~e~(max)M
5.12GeV)1(~E
Mln2
6.25X
T
X
Mass range of central diffraction (DPE) scales like √s, ~ 0.05 √sAt ISR, 3 GeV / 63 GeV … resonances, glueball searchAt Tevatron, 100 GeV / 1960 GeV … jetsAt LHC, 500 GeV/10TeV 700 GeV/14 TeV … WW, ZZ, H …
28Mike Albrow Diffraction in High Energy Collisions CERN June09
Central Exclusive Production (AFS at ISR)
Structures not well understoodbeyond f(980). Not studied at higher
No ρ
0 (980)f
All σ cut by f0?
G(1500)??
s
G PC + ++I J =0 even
Coherent scatteringα stay intact. In LHC Au + Au(e.g. ALICE):
can be IPor photon(more likely)
Au
AuAu may also fragment
29Mike Albrow Diffraction in High Energy Collisions CERN June09
Central diffractive production or Double IP Exchange at Tevatron
M(max) ~ 100 GeV : Jets
pmeasured in Roman pots
Rapidity gap>~ 4 units
Q: Is IP just a soft mush of q and g, or sometimes leading g + colour bleaching?Di-Jet mass fraction needs a “hard” component, with IP ~ 1 gluon + soft g/gg/…
30Mike Albrow Diffraction in High Energy Collisions CERN June09
Component of pomeron that is leading gluon
g + g J + J g + g g + g g + g H c b
c-loopb-loopt-loop
H
b
c
p + p p + H + p @ LHC& nothing else produced!
p + H + p should happen at a detectable rate:Measure p very precisely mass of central state (e.g. H) σ ~ 2 GeV
Central state must have C = +1, P = +1, Even spin (0, 2 distinguishable)Width can be measured if > ~ 3 GeV. Close states (e.g. h, H in SUSY) can be separated.
Need precision measurements of protons, together with central H-like event.
Even g + g γ + γ
50%
410~
p
dp
31Mike Albrow Diffraction in High Energy Collisions CERN June09
Central Exclusive Production
pp p + X + p where X is a simple system completely measured
p p At CERN ISR
Glueball Search
At Tevatron & LHC
gg through q-loops (box) + color bleaching (g)
W
W
; ,
; ,
WW H WW H ZZ
H bb BSM WW SUSY etc
IP IP G
bc ,
32Mike Albrow Diffraction in High Energy Collisions CERN June09
32
Exclusive Di-Jets
“Almost” exclusive di-jet,Two jets and nothing else
0.8JJ
CEN
M
M
(~ polar angle)
(azimuth) Transverse
Energy TE
JETJET
else nothing~ pJJppp
Observed in CDF, QCD tests& related to p+H+p
Interesting QCD: gap survival, Sudakov factor Nearly all jets should be gg …. qq suppressed by M(q)/M(JJ) (Jz=0 rule)
Gluon jet physics.
p JJ
GAP
JJJJ
X
MR = 1.0
M
33Mike Albrow Diffraction in High Energy Collisions CERN June09
33
c0c
J/ψ
γ
μ+
μ-
& nothing elsein all CDF
-7.4 < |η| < + 7.4
Added to CDF: Beam Shower Counters BSC:Scintillator paddles tightly wrapped around beam pipes.Detect showers produced in beam pipes if p or p dissociate.e.g. 8 + 10 counters
If these are all empty, p and p did not dissociate (or BSC inefficient, could estimate from data)but went down beam pipe with small (<~ 1 GeV/c) transverse momentum.
pp
4.7||2.5
CDFcentral
BSC (size greatly exaggerated!)
- 50 m
CDF measured exclusive c J/ψ + → μ+μ-
34Mike Albrow Diffraction in High Energy Collisions CERN June09
pppp
402 events
35Mike Albrow Diffraction in High Energy Collisions CERN June09
Now allow photons: EmEt spectrum with J/ψ mass cut:
Empirical functional form
MC also estimates only few % of under the cut
65 events above 80 MeV cut.3 events below (estimated from fit)4% background under J/psi# = 65 +/- 8
4039:not do ψ(2S)
352286 :photons have J/ψ
γJ/ψχ c
cχ
γJ/ψχ c
several""factor y Uncertaint
nb 90 :prediction (Durham) KMR
nb101078| 0 ydy
d
36Mike Albrow Diffraction in High Energy Collisions CERN June09
Dimuons: Upsilon Region
Invariant Mass 0 associated trackspT(μμ) < 1.5 GeV/c
CDF Run II Preliminary
CDF Run II Preliminary
Trigger: μ+μ- |η|<0.6 , pT(μ) > 4 GeV/c
Inclusive
Search for/measurement ofphotoproduction of Y, Y’(not before seen in hadron-hadron)
Status: Candidates:analysis in progress.QED continuum checkY : cf HERA (we resolve states)Can we see ?
Y(1S)
Y(3S)
Y(2S)
γΥχ b
37Mike Albrow Diffraction in High Energy Collisions CERN June09
Categories of Diffraction at LHC
p
s2ln 19.2 (cf 15.2 at Tevatron)
my
Can have a 4-unit gap with 2 TeV SD
Can have (VF)J – G6 – (VF)J
Can have 2 x 3-unit gaps with 700 GeV DP
Can have p-G3-X-G3-X-G3-p with M(X) ~ 12 GeV
38Mike Albrow Diffraction in High Energy Collisions CERN June09
Exciting the vacuum with photons
γ Doesn’t work!E-p conservation forbids it;except for v. short times(evanescent)
γγ
Does work!E-p conservation allows it;Energy injection promotes loop to reality.
Heirarchy: ,...?tt,W,...Wμμetc.),π(&qq,ee 0
γ
γ
How do e,μ,τ,q…know what mass to have?
39Mike Albrow Diffraction in High Energy Collisions CERN June09
Photon “beams” radiated from electrons and protonsLEP etc: e+e- (~ background free)HERA: e p (more background, little done)pp/ ppbar: Very high b/g … Seen in CDF γ
e,p
ee
Phys.Rev.Lett 98,112001(2007)
2GeV/c)μM(μ
μμ
PRL 102, 242001 (2009)
PRL May 2009
μμeeμμ
inel12σ103~pb0.24~σ
Tevatron as a collider!
40Mike Albrow Diffraction in High Energy Collisions CERN June09
E not ET!
CLC BSC
M(ee) = 49.3 GeV/c2 |Δφ-π| = 6 mrad = 0.34 deg, pT(ee) = 210 MeV
M reach Tevatron >~ HERA, LEP !M reach LHC ~ 300 GeV –ishIncludes γγ → WW (~ 50 fb)
pb 0.256QED cf
pb 24.0
4||,GeV/c40
)(
(LPAIR)
13.010.0
2
μμor
M
peeppp
High mass γγ→e+e- event in CDF
41Mike Albrow Diffraction in High Energy Collisions CERN June09
All our measurements agree with QED: So what?
1) It shows we know how to select rare exclusive events in hadron-hadron environment2) No other h-h cross section is so well known theoretically except Coulomb elastic (inaccessible).
Probably best possible Luminosity calibration at LHC e.g.3) Outgoing p-momenta extremely well-known (limited by beam spread). Calibrate forward proton spectrometers.4) Practice for other γγ collisions at LHC:
.,..~~
,WWγγ ll
2 |η| and GeV 10)μM(μ
withpb500in events 4400-
1
Luminosity calibration at LHC
42Mike Albrow Diffraction in High Energy Collisions CERN June09
Khoze, Martin and Ryskin, hep-ph/0111078, Eur.Phys.J. C23: 311 (2002)KMR+Stirling hep-ph/0409037
36 fb
-1T~ 40 events per fb with p (γ) > 5 GeV/c & |η| < 1.0
& much smallerqq
Exclusive 2-Photon Production
Tevatron
Claim factor ~ 3 uncertainty ; Correlated to p+H+p
H
Phys.Rev.Lett. 99,242002 (2007)
TE ( ) > 5 GeV; | ( ) | 1.0 3 candidates, 2 golden
12Note : 2 10 !MEAS INEL
43Mike Albrow Diffraction in High Energy Collisions CERN June09
Exclusive Z production : CDF SearchAllowed in SM (like V)but ~ 0.3 fb (Motyka+Watt)
Could be enhanced by BSM loops
2.2/fb : 318K μμ&ee M > 40 GeV; 183K in Z window 82-98 GeVRequire no other interaction, no additional tracks, all calorimeters in noise (E)
8 with BSC empty
Interesting?!-IP-Z eff.coupling.ZOOM IN to see how!
LHC) @ (13fb
0.3fbTheory )σ(Z
C.L.) (95% pb 0.96)σ(Z
excl
excl
~ record E()
44Mike Albrow Diffraction in High Energy Collisions CERN June09
Central Exclusive Production of Higgs ?
Higgs has vacuum quantum numbers, vacuum has Higgs field.So pp p+H+p is possible in principle.Allowed states:
Process is gg H through t-loop as usualwith another g-exchange to cancel colorand even leave p’s in ground state.If we measure p’s (4-vectors):
H
2CEN 1 2 3 4M ( )p p p p
+ - ±Even for H W W l νJJ !
Aim: to be limited by incoming beam momentum spreadRealistic; ~ 2 GeV
p -4σ10 0.7 GeV
p
PC ++I J =0 even
J >= 2 strongly suppressed at small |t|
t
( ) 2 GeV per eventHM
45Mike Albrow Diffraction in High Energy Collisions CERN June09
Features of pp p + H + p at LHC
1) S:B can be high, > 1, even for H bb
2) Mass resolution ~ 2 GeV/event, for any final state
3) Quantum numbers determined, e.g.
4) If width >~ 3 GeV, directly measure width.
5) In MSSM can have close h,A,H. Then A excluded, h-H resolved.
6) If
0 (and 1 forbidden)CPJ
11 10 30Ae 300Ae events in 30
(Ae = Acceptance × efficiency 30%)
10 100 events (SM; maybe more in BSM)
fb fb
di-jets are suppressed by 0 rulezbb J
46Mike Albrow Diffraction in High Energy Collisions CERN June09
Central Exclusive H Productiongg fusion: main channel for H production.
Another g-exchange can cancel color, even leave p intact. p p p + H + pTheoretical uncertainties in cross section, involving skewedgluon distributions, gluon k_T, gluon radiation, Sudakov ff etc.
+ - + -
2 2 21 2 3 4 H
H(160) W W p e μ p
MM ( ) M
T
p p p p
Nothing elseon emu vertex!
Price ~ 1/2000 – 1/10000 σ (excl) ~ 1 – 10 fb cf ~ 20 pb
47Mike Albrow Diffraction in High Energy Collisions CERN June09
FP420 : Forward Protons 420m & 240m from CMS & ATLAS
CMS
CMS: Inner Vacuum Tank insertion
420 & 240m 240 & 420m||| ||| ||| |||ATLAS
; ,
; ,
WW H WW H ZZ
H bb BSM WW SUSY etc
ATLAS
48Mike Albrow Diffraction in High Energy Collisions CERN June09
~ 8 m
pBEAM
BPM BPMQUARTIC
~ 8 layers10um x-ypixels
3 mm
ResolutionRad hardnessEdgelessnessSpeed, S/NAvailabilityEnthusiasts!
TOF
Z
( ) 4.2 2.1 mm
cf (interactions) 52 mm
z
6mm(y) x 24mm (x) covers distribution
GASTOFMCP
QUARTIC
FP420 = Forward Protons 420m from x … also 240m under study
Best ever spectrometers!420 m vacuum, 120m 8T dipoles, ~10μm origin (x,y), 1 μrad track
3D- silicon ~ 8 μm over 8m.Fast timing P-U reduction factor ~ 25Normal low-β, design for 10^34
Detector area6mm x 24 mm
32.1
2
mmmm
420m too far for L1 triggerlatency. 240m not, but > M. inefficient, other channels OKbb
49Mike Albrow Diffraction in High Energy Collisions CERN June09
H[ ](M ), s = 14 TeVpp p H p
What is exclusive H cross section?
Calculation involves:gg H (perturbative, standard, NLO)Unintegrated gluon densitiesProb.(no other parton interaction) (“Gap survival”)Proton form factorProb.(no gluon radiation no hadrons) Sudakov Suppression
( ). ( ')i ig x g x
Durham Gp: Khoze, Martin, Ryskin, Stirlinghep-ph/0505240 ++
σ ~ 3 fb (M(H)=125 GeV)“factor ~ 3 uncertainty”
100 fb^-1 ~ 100-1000 Ae events(Ae = acceptance, efficiency)
Other estimates differed by “large” amounts! But exclusive c etc is a check.
Exclusive
50Mike Albrow Diffraction in High Energy Collisions CERN June09
Cross section for p+p p + SMH + p at LHC, x branching fractions:
Small (~ fb) but S:B can be high.
ExHuMe “verified” by 2-photon, & JJ < 140 GeV : bbar, > 140 GeV : WW(*)
FP420 Acceptance fn. Mass: (a) 420+420 (b) 420+240
(a) (b)
c
51Mike Albrow Diffraction in High Energy Collisions CERN June09
Simulations of SMH b-bbar signals & backgroundCox, Loebinger and Pilkington arXiv:0709.3035 (JHEP)
(a) (b)
(a) 300/fb = 3 years at 10^34, 420+420, L1 trigger on jets, muons, 25 kHz(b) Same with no pile-up background – very high resolution p-timing
... and if 420+420 in L1 trigger
future upgrade in latency?
52Mike Albrow Diffraction in High Energy Collisions CERN June09
l
J J
p p
JJM
WW*
Can use ~ 50% of WW (all but JJJJ)
, , ,WW l JJ l e SMH(135-200) WW(*) … Various missing masses
!! Unfortunatelyvery few events (SM)
Durham Gp: Khoze, Martin, Ryskin, Stirling hep-ph/0505240
(*)
(*)
(12 34JJ ) 0( )
(12 34JJ) (even for )
( )
W
W
MM l M
MM M
M JJ M
H(180) ZZ (BR ~ 10 )
(12 34 ) ( ), ~ 2 GeV!M
l l l l l l
MM l l M Z
μ(W)WWγγ Also (50fb)
53Mike Albrow Diffraction in High Energy Collisions CERN June09
Non-SM cases : no Higgs? MSSM Higgses?
1) No SMH? Can we exclude? Suppose measure 100 exclusive in CMS. (M() > 10 GeV) predict p+SMH+p to ~ 20% (trigger study in progress) Suppose expect (say) 100 pHp events in 30 fb^-1, see < 40. Conclusion?
2) No SMH or MSSM-Hs? WW physics becomes very interesting!
+ -
WW
via 50fb (precisely known in SM)
dW W Final State Interactions distort , visibly? New physics?
dM
pp p W W p W W
W
fsi
3) In case of SUSY, Forward p-tagging can be crucial! Cross section can be much higherthan SMH. Decays to enhanced.A(CP –ve) highly suppressed.
bb
Kaidalov Khoze Martin Ryskin hep-ph/0307064
Preview of ILC/CLIC physics
54Mike Albrow Diffraction in High Energy Collisions CERN June09
Can have {h, A, H} close together in mass (few GeV)Hard to resolve by inclusive production.
Exclusive advantages: higher production than SM, A highly suppressedExcellent mass resolution could separate h and H (unique)
Excellent mass resolution could even measure H widths (if ~ few GeV)
J.Ellis, J.S.Lee and A.Pilaftsis, PRD71:075007, hep-ph/0502251Durham Group (KMRS)
MSSM
H
h
A
55Mike Albrow Diffraction in High Energy Collisions CERN June09
Summary
Strong Interaction well understood at large Q2 (QCD)but most interactions difficult to describe:Total cross sections, elastic scattering, diffraction dissociation…Regge theory has some validity but connection to QCD obscure.
Hard interactions : Jets, W, Z … provide a tool (probing pomeron)
Pomeron has a hard component: g (most momentum) + (soft) g/ggThis allows ~ “tagged gluon beams” at LHC, & γ-beams
Measuring p + p p + X + p new window on SM & BSM physics
....,~~
,,,, llHhWWllXFP420/240 project in CMS & ATLAS
Warm-up: Measure diffractive JJ, W, Z, γγ at LHC
56Mike Albrow Diffraction in High Energy Collisions CERN June09
Thank you
Back-ups
57Mike Albrow Diffraction in High Energy Collisions CERN June09
e.g. Schafer and Szczurek: arXiv:0705.2887 [hep-ph]
Some predictions for J/psi photoproduction: Machado,Goncalves 3.0 nbMotyka and Watt: 3.4 +- 0.4 nbSchafer & Szczurek ~ 2.8 nbNystrand 2.7+0.6-0.2 nb
Our result: 3.92 +- 0.62 nbTak
e 3.
0 +
- 0.
3Y is much lower.Allow Pile-Up (x 10)More data (x 3)More Δy (x >4)
(95%) J/ψOIPfor nb 2.3 )(J/ 0y|dy
dσ
(CDF) nb 0.623.92)(J/ψ 0y|dy
dσ
average)(theory, nb 0.33.0)(J/ψ 0y|dy
dσ
Our limits on O-exchange are close to,and constrain, theoretical predictions
58Mike Albrow Diffraction in High Energy Collisions CERN June09
Summary of Results pppp M = 3-4 GeV/c2
(IP)p(γγp TT
No strong evidence for odderon
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