in the r-parity violating susy model at hadron colliders 张仁友 中国科学技术大学
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Xepppp /in the R-parity violating SUSY model at hadron colliders
张仁友中国科学技术大学
R=(-1)2S+L+3B
SUSY new parity
partially R-parity violation (RPV) i.e. non-simultaneous L and B violation in general super-potential
Phenomenology: + neutrino-oscillation + stable Proton + scalar sneutrino resonance production and LFV decay
2
1 1ˆˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ2 2p
a b a b a bab i j k ab i j k ijk i j kijk i ab i iR jkW L L E L Q D U D D L H
Theoretical Motivation
’
LFV process @Tevatron/LHC:
--- sneutrino resonance effect in e can be experimentally detected
sneutrino contribution (s-channel) squark contribution (u-,t-channel)
eeqqppp )(
--- s-channel decouple with u-channel 0ˆˆ ts MM
Two decoupled contributions of sneutrino and squark:
CompHep + Pythia
d of einclusive
Not back-to-back!---
--- Large luminosity at the LHC glupn-gluon fusion subprocess!
--- the QCD correction is quite significant in the high PT region!
kinematic cuts:
Why need NLO QCD corrections?
GeVPTe 30 GeVPT 25
Contributions up to O(s) NLO
1.The Leading Order cross section
2. Virtual O(s) one-loop corrections
3. Real gluon emission corrections
4. Real light-quark emission corrections
5. Higer order gluon-gluon fusion contribution
Numerical result Inputs:
-- K-factor vs sneutrino mass at Tevatron and LHC
1.28~1.79 Tevatron1.32~1.58 LHC
-- Distribution of the transverse momentum of positron
NLO QCD correction
CompHep + Pythia d of einclusive
-- gluon fusion contribution
Large luminosity of soft gluon will contribute to low mass region
<1%GeVPTe 30 GeVPT 25
-- Distribution of the electron-muon invariant mass
a high threshold cut on electron-muon invariant mass !
1. The first two generations of sneutrino are much heavier than the third one.
In order to simplify calculation, we take following assumptions:
2. Applying a high threshold cut on electron-muon invariant mass.
(50 GeV)
3. Applying the naive fixed-width scheme in the sneutrino propagator.
(10 GeV)
4. Setting decoupled squark and gluino section.
(1 TeV !)
In our investigating parameter space the K-factors varyin the ranges of [1.182,1.643] and [1.335,1.614] at theTevatron and the LHC, respectively.
Uncertainty investigation
The relative error of K-factor induced by the factorization scale:
0.17%(3.1%) 100 GeV1.8% (1.3%) 250 GeV3.0%(0.46%) 500 GeV
The relative error of K-factor induced by the PDF:
6.0% (5.8%) 100 GeV7.8% (5.0%) 250 GeV14.2%(5.9%) 500 GeV
-- qT distribution
Conclusions
1. K-factor to be 1.2 ~ 1.8 at Tevatron and LHC; the main uncertainty comes from pdf.
2. High order gluon fusion should be accounted @LHC.
3. The distribution of the transverse momentum of final e-muon pair by resummating the logarithmically-enhanced terms for soft gluon can be a reference for future experimental analysis.
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