mike albrowrencontre de blois may 2005qcd and hard diffraction at the lhc 1 introduction: qcd at the...
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1Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
QCD and Hard Diffraction at the LHC
Introduction: QCD at the Tevatron (overview)
The High Q^2 Frontier: Jets, tops, W/Z, Q or X?
LHC: A new arena for QCD. Detectors
Very High Mass Diffraction
High Mass “Central Production” (a.k.a. DPE)
The FP420 Project
2Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Recent QCD studies at the Tevatron (CDF & D0)
Every interaction is QCD!+ - + -{Exception: pp p e e p, p W W p}!
In May 2003 – May 2005 CDF (D0) published 43 (10) “QCD” papers:
pp and pp
other topics to follow...
... even that!
2T S
T
ch
2S
JETS: Production cross section (E ,η, s) and α ( )
Jet Algorithms: cone, k
Jet shapes/structure: n , fragmentation, q/g differences, c/b content
3-jet events and α ( )
(JJ)
Q
Q
3Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
T
0 (')S
+ -
Particle production cross sections (tot, p , η, s)
Strongly interacting: K , Λ, c(D), J/ψ , B, BB, , t t
Not S.I. : γ, e e , W, Z, (& F-B assymetries), VV (all 6 combs)
0 0 * + -S
b
Hadron decays (B-hadrons, lifetimes τ and BR's) :
B , J/ψ ; B had, γX, J/ψX, J/ψK π π
( / )J
+ +S
c
Hadron spectroscopy :
(3872) J/ψ
(D -D )
B J/ψ π (CDF discovery)
Pentaquark searches (negative)
X
m
ch T
Underlying event:
n ,p etc in soft vs hard collisions
... in jet events
[in WW, (in general in V and VV events)]
Diffraction / rapidity gaps:
Diffractive production of dijets, J/ψ
DPE inclusive [GXG], double gaps:[xGxGp]
QCD Topics in TeVPublicationsMay 03 – May 05
2T S
T
ch
2S
JETS: Production cross section (E ,η, s) and α ( )
Jet Algorithms: cone, k
Jet shapes/structure: n , fragmentation, q/g differences, c/b content
3-jet events and α ( )
(JJ)
Q
Q
4Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Jets
Angular (or y) distributionswell fit (log scale!) ... buty = 2.4 still “central”
Below 50 GeV mostly gg (at y=0)Above 400 GeV mostly q-qbar
Can study g and q fragmentationAt LHC pp p JJ p ~ pure gluons
1~ Run 2 expectation
40th
Cone algorithm
5Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Run 152507 Evt 1222348
All hits/tracks tracks pT > 2 GeV/c
At the top of the spectrum:
618 GeV
552 GeV
CDF kT algorithm
6Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Here is a beautiful 3-jet event!
155 GeV
402 GeV
444 GeV
Tp (tracks) > 2 GeV/c
ET > 0.5 GeV
Run/Event 162498/4411694
7Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Projected Jet Cross Sections at LHC
Spectra drawn to few/100GeV bin in 100 fb^-1
Let us hope these are quite wrong:Peak(s), excesses, cut-off (black hole production?) --- the end of high pT physics!
8Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Coverage in (x,Q2) extended by more than an Order of Magnitude
Smallest x requires veryforward detectors:
2 8 2 1810 GeV d 2.10 cmQ
1x 2x
*
EVENTSHOWN
9Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Production Cross Sections Rise Strongly with Energy
(Except at fixed x)
~ 1 top/secat 10^33
10Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
BFKL and Mueller-Navelet Jets
Color singlet (IP) exchange between quarksEnhancement over 1g exchange – multiRegge gluon ladderJets with large y separationn 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
Very forward calorimeters OS
11Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Berger, Qiu, Wang, hep-ph/0404158
D0 Run II Y-production
Cacciari, Frixione, Mangano, Nason, Ridolfi, hep-ph/0312132
CDF B-hadrons Run IICDF, hep-ex/0412071
TeV 03-05T
0 (')S
+ -
Particle production cross sections (tot, p , η, s)
Strongly interacting: K , Λ, c(D), J/ψ , B, BB, , t t
Not S.I. : γ, e e , W, Z, (& F-B assymetries), VV (all 6 combs)
12Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
0 0 * + -S
b
Hadron decays (B-hadrons, lifetimes τ and BR's) :
B , J/ψ ; B had, γX, J/ψX, J/ψK π π
( / )J
SFirst Observation B
5SBR(B ) [1.4 0.6(stat) 0.2(syst) ± 0.5(BRs)] 10
u,c, t
Penguin diagram
TeV 03-05
W
13Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
CDF-7142
0 + - 6dBR (B π π ) = 5 ×10
Rare Charmless B decays
0 0* -5dBR (B K ) =1.1×10
0dB
At LHC: LHC-B +ATLAS/CMS?
14Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
+ +S
c
Hadron spectroscopy :
(3872) J/ψ
(D -D )
B J/ψ π (CDF discovery)
Pentaquark searches (negative)
X
m
*Future : ,c c cB B B
pQCD !
cIP(gg)IP(gg) B BDX ?
TeV 03-05
15Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Probing Very Small x Gluons
High parton densitiesNew phenomena (gluon saturation)HERA measures q(x) to ~ few 10^-5 g(x) by evolution, charmLHC : measure g(x) to < ~ 10^-5more directly
Instrument few degree region with tracking, calorimetry (em+had), muons, , jets, photons ... CASTOR, TOTEM
/J
1 2 1 21 2
0T 1 2
51 2
x ; x
e.g. s=14 TeV, p = 5 GeV, y = y =4 (2.1 )
x 0.08, 1.4 10
y y y yT Tp pe e e e
s s
x
16Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
ch T
Underlying event:
n ,p etc in soft vs hard collisions
... in jet events
[in WW, (in general in V and VV events)]
CDF study: charged particles transverse to high pT jets
MPS
TeV 03-05
17Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Beyond Single Parton Distributions
Double and multiple parton scattering
Hint at ISR (4 “jets”), Seen in UA2 and CDF γ + JJJ
(qg) + (qg) cc/bb
& Double Drell-Yan : diquarks – anti-diquarksCorrelations in b (impact parameter) and x
18Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Diffraction / rapidity gaps:
Diffractive production of dijets, J/ψ
DPE inclusive [GXG], double gaps:[xGxGp]
But before May 2003:
T 2
dσ dσσ , , (SDE)
dt dM dtSDE JetJet,J/ ,b,W,Z
DPE JetJet
Jet-Gap-Jet [JGJ]
TeV 03-05
19Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
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
20Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
QCD
Google tev4lhc
Fermilab Sept 2004BNL Feb 2005CERN Apr 2005Fermilab Fall 2005
21Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
ATLAS
Very small person (?)
A “QCD machine”, especially if add forward detectors!
22Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
23Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
CMS at LHC
Bigger people!
24Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
(MWPC TRACKING) CASTOR
25Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Detecting Protons with xF > 0.9
K.Eggert’s talk
26Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
0c
0b
u-loop : γγ c-loop : χ
b-loop : χ t-loop: H
Central Exclusive 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.Probably ~ 0.2 fb at Tevatron, not detectable, but should be possible at LHC (higher L and ~ 3 fb?)
( )SMH
0 0c b
Theory can be tested, low x gluonic
features of proton measured with
exclusive γγ, χ and χ production.
at Tevatron
100 x Acc events in 30 pb^-1
27Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Central Exclusive Higgs Production
Can be inclusive (soft central hadrons) but exclusive (nothing else)is most interesting. Precision measurement of both p M(central) by MM
Possible resolutions (~ 250 MeV at Tevatron) ~ 2 GeV at LHC.
Can go for dominant H(110-130) b-bbar decay mode
Exclusive DPE q-qbar dijets strongly suppressed (Jz = 0 rule)
Selection Rule on central Q.Nos:Scalar ... p correlations confirm (need statistics!)
Non-SM H interesting!
G PC + ++
G PC + ++
I J = 0 0 dominant esp. as t 0
I J = 0 2 next
2 2central 1 2 3 4M ( - - ) ; 4 - vectorsip p p p p
28Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Acceptances vs Mx for p + p p + Mx + p
In addition to 215m (TOTEM)420m detectors are
essential for Mx < 400 GeV... region of H, WW, ZZ
Both ATLAS & CMS want this.Join forces: FP420 project
LOI for R&D LHCC June 05
29Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
FP420 = Forward Protons at 420 m
Groups in ATLAS and CMS/TOTEM want to addvery forward proton detectors, mainly to study “DPE”, central production.Central states especially : WW, ZZ, H, bb, t t, jet-jet, X ...
FP420
FP420
Valentina Avati
Inelastic protons bent few mm out of beam6mm x 24 mm detector (e.g. Si pixel)
25 mm
10 mm
TOTEM
TOTEM
30Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Albert De Roeck
US
31Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Diagrams for Prompt VV Pair Production in pp/ppbar
Note different color flows in thesediagrams can give differenthadronic activity.(a) and (b) have color 3 annihilation(d) has color 8 annihilation(c) and (e) have color singlet exchange. (c) high pT q – forward jets; (e) low pT p’s – no jets, can be exclusive
(Prompt i.e. not from top and not from Higgs)
+ +
a) Any 0,1 pair. 90% of WW at TeV, less at LHC
b) Only γW, WW, WZ
c) Any pair (even W W ).
Negligible at Tevatron, larger at LHC
d) Negligible
e) Eventually dominant if White is right!
Q
1 2
Also γγ ~ 100 fb
Discriminant : t , t
W W
32Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Cross section for WW Production: Energy Dependence
Tevatron cross section agrees with CTEQ NLO
Tev2 sig(ZZ) = 1.39 pbsig (ZW) = 3.65 pbsig WW = 12.4 pb
LHC ~ 10 x higher
If Tevatron RoT apply,At LHC :SD, ~1% ~ 100 fbDP, ~ 10^-3 ~ 10 fb
i.e. Guesstimate for DPE WW (ZZ) + anything ~ 10 (1) fb
33Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Central Exclusive WW Production at LHC
+ - + -
2 2 21 2 3 4 H
H(160) W W p e μ p
MM ( ) M
T
p p p p
Nothing else on 2-lepton vertex!μ
e
+ White Pomeron search
eμ
2 2invisible 1 2 3 4 visible
See invisible Z νν e.g. in H ZZ
M ( - - )
Distinguish ZZ
from WW
p p p p p
Also W W
34Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Double Pomeron W+W- via Q6 Loop
Photon-Pomeron-Z vertexvia Q6 loop
Photoproduction at LHC?pp {p Z p}γ IP
~ 0 in SM
35Mike Albrow Rencontre de Blois May 2005QCD and Hard Diffraction at the LHC
Summary
Tevatron is, and LHC will be, a cornucopia of QCD physics
At LHC, 2 2Q ~ 0.001 ~ 50,000,000 GeV
Jets, W, Z, b, c, production, spectroscopy, decaysand especially:
rapidity gaps, exclusive production of jets, H, WW, ZZ, BSM
Very Forward Proton Detection – New window on strong and electroweak interactions