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.