Theory phenomenology UU

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Theory / phenomenology _at_ UU
Gunnar Ingelman

• QCD perturbative ? nonperturbative
• model for PDFs
• small-x dynamics, DGLAP?BFKL
• soft rescattering
• diffraction
• jet quenching in q-g plasma
• colour fields structure strings

THEP 2004

• Beyond Standard Model
• Higgs models
• 2HDM, alt. heavy Higgs
• supersymmetry
• charged Higgs bosons, CP-asym.
• QCD in MC for BSM-processes
• matching ME-PS

• Astroparticle physics
• neutrino flux from cosmic ray interactions
• moon as detector for ultrahigh-energy neutrinos
• Tool Monte Carlo event generators

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THEP group _at_ IKP/UU
Johan Rathsman fo-ass ? lektor
Johan Alwall ? postdoc SLAC
Nic Timneanu ? forskare biofysik
Leszek Motyka postdoc ? DESY

• Rikard
• Enberg
• postdoc
• Berkeley

2004
2005
Magdalena Larfors ? doktorand teor. fysik
GI
Korinna Zapp ? doktorand Heidelberg
David Eriksson doktorand
Stephan Hesselbach postdoc ? Würzburg
Oscar Stål doktorand
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QCD Model for Soft Colour interactions (SCI)
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Gap-size is infrared sensitive observable !
Size ?ymax of largest gap in DIS events

• Large gaps at parton level
• Normally string across
• hadrons fill up
• SCI ? new string topologies,
• some with gaps

Gap events not special, but fluctuation in
colour topology /hadronisation SCI model (1
parameter !) fits hard diffractive data at HERA
and Tevatron Captures most essential QCD
dynamics ? theory emerging
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QCD factorisation and rescattering
QCD factorisation theorem ? hardsoft separation
? parton density fcn Expanding the Wilson line
i.e. rescattering of the struck quark via
longitudinal (A) gluons instantaneous in LF
time x t z, within Ioffe coherence length
1/mpx
Leading twist exchange between hard partons and
target spectators Measured PDFs include
rescattering !
Brodsky, Hoyer et al.
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QCD rescattering as basis for SCI model
Brodsky, Enberg, Hoyer, GI, 2005
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QCD Jet quenching ? Quark-gluon plasma !?

• Test if quark-gluon plasma formed in
• central, high energy AuAu collision at RHIC
• High-p? parton from hard 2?2 pert. QCD
• interacts with plasma and loose energy
• ? Jet energy quenched,
• fewer high-p? particles
• (relative to pp)
• Soft Colour Interaction model
• K. Zapp, UU-Heidelberg collaboration
• energy loss from elastic scattering
• gives ? half observed effect
• Add medium-induced gluon radiation,
• considered previously as dominating
• ? Best evidence for QGP !?

Hadron flow in azimuth ?? relative to trigger
particle/jet
AuAu _at_ RHIC
peripheral
central
Disappearence of back-to-back jet !
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QCD Gaps between jets ? BFKL dynamics
Enberg, GI, Motyka
Numerical solution of BFKL eq. with non-leading
corrections using Pythia MC reproduces data

• Large momentum transfer t pT2 -jets
• ? hard pert. QCD exchange
• Elastic parton-parton scattering by
• hard colour
• singlet exchange
• High energy limit
• s/t gtgt 1 ? amplitude
• dominated by terms
• resummed by BFKL

ET and ?? dependences OK asymptotic Mueller-Tang
? wrong ET-dep. Normalisation OK, correct gap
survival prob. with SCI model that destroys gaps
!
Provides strong evidence for BFKL dynamics !
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QCD QCD in charged Higgs production _at_ LHC
Two factorisations / approximations 2? 2
process g b ? H? t with initial b-quark PDF
from g ? bb via DGLAP resumming collinear logs
? better description at small pTb and
total cross-section
2? 3 process g g ? H? tb NLO ME ? better
description at large pTb of b-quark But, when b
collinear ? double counting
Match by subtracting double counting term
1st log in b-quark PDF
Add-on to PYTHIA
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Astroparticle Physics
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? 1 GHz H 100,250,1000 km
? 0.1 GHz H 100,250,1000 km
Oscar Stål et al. astro-ph/0604199

• Overall better flux limits, in particular for
  lower frequencies
• GZK neutrinos hard to catch, lower threshold
  required
• Exotic sources within reach

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Outlook for LHC era
Beyond Standard Model phenomenology
!! Connection to astroparticle physics
Collaboration between LHC and astroparticle
communities QCD important in Beyond SM processes
and in backgrounds, as well as in its own right
! Monte Carlo developments as powerful tools
needed
THEP 2004