# Presentation: 043347

## The Smoking Gun of Baryon Number Violation

- P. Skands

## Baryon Number Violation (BNV) in SUSY
Implementation of 2- and 3-body decays in the PYTHIA generator
BNV Colour Topologies
Baryon Number Violation and String Topologies
An explicit detailed model  baryon number flow
Properties and predictions
Summary and Outlook

- Baryon Number Violation (BNV) in SUSY
- Implementation of 2- and 3-body decays in the PYTHIA generator
- BNV Colour Topologies
- Baryon Number Violation and String Topologies
- An explicit detailed model  baryon number flow
- Properties and predictions
- Summary and Outlook

- The Smoking Gun of Baryon Number Violation

## R, B, or L? (Fast-forward)

- Decent physics case + interesting to explore phenomenology

-  Most general MSSM Superpotential:

## Collider Phenomenology

- General problem: how to obtain fully exclusive descriptions of collider final states (in any physics model, SM or BSM)

- Non-Perturbative
- hadronisation, colour reconnections, beam remnants, non-perturbative fragmentation functions, pion/proton, kaon/pion, ...

- Soft Jets + Jet Structure
- Multiple collinear/soft emissions (initial and final state brems radiation), Underlying Event (multiple perturbative 22 interactions + ... ?), semi-hard separate brems jets

- Resonance Masses ...

- Hard Jet Tail
- High-pT wide-angle jets

-  & Widths

- + “UNPHYSICAL” SCALES:
-  QF , QR : Factorisation & Renormalisation

- s

- This has an S matrix expressible as a series in gi, ln(Q1/Q2), ln(x), m-1, fπ-1 , ...
**To do precision physics**:
- Need to compute and/or control all large terms
-  EVENT GENERATORS

**Inclusive**

**Exclusive**

- Hadron Decays

## Implementation of 2- and 3-body decays in PYTHIA 

- Implementation of 2- and 3-body decays in PYTHIA

- Partial widths: LO ME’s, (only 3rd gen massive)
- Kinematics: isotropic 3-body (good when intermediate states very off shell).
- Final state parton multiplicity increased by subsequent showers
- NB: only MSSM pair production included (no single sparticle production)

- Dreiner, Richardson, Seymour:
- JHEP 04(2000)008

## Baryon Number Violation (BNV) in SUSY
Implementation of 2- and 3-body decays in the PYTHIA generator
BNV Colour Topologies
Baryon Number Violation and String Topologies
An explicit detailed model  baryon number flow
Properties and predictions
Summary and Outlook

- Baryon Number Violation (BNV) in SUSY
- Implementation of 2- and 3-body decays in the PYTHIA generator
- BNV Colour Topologies
- Baryon Number Violation and String Topologies
- An explicit detailed model  baryon number flow
- Properties and predictions
- Summary and Outlook

- The Smoking Gun of Baryon Number Violation

## Colour Topologies

- Confinement potential: non-perturbative breakups  hadrons
- Not a priori calculable  QCD-inspired phenomenological models
- Semi-classical, based on colour dipoles: “Clusters” or “String pieces”

- Basic problem easy to understand:
- No dipole!

- blue

- antiblue

- green

- red

- blue

## String Topologies

- How does the system hadronize?
-  Assume vacuum still acts as dual colour superconductor colour vortex lines ~ string picture still applicable
-  Q then: **which** string topology? Y, Δ, V, ... ?

- Montanet, Rossi, Veneziano : Phys.Rep.63(1980)149

- &

- Minimization of potential energy ~ string length (V(r) = κr)

-  Picture of Y-shaped topology with ‘string junction’

- junction

## The Junction

- How does the junction act / move?

- LAB
- Boost
- JRF

- Inverse boost  handle on motion of the baryon number, _*through*__ fragmentation_

- T. Sjostrand, PS Nucl.Phys.B659(2003)243

## Hadronisation

- ‘junction baryon’

- Technically: 2 least energetic strings fragmented outwards-in
- When little energy left, remains collapsed into diquark
- remaining qq – q string piece fragmented as usual
- Note: _**baryon number**_ can be entirely separated from _**leading flavours**_

- T. Sjostrand, PS Nucl.Phys.B659(2003)243

## (More Complicated Topologies)

- 2 possibilities:
-  a) 2 junction baryons
-  b) junction-junction annihilation
- Select between a/b based on which topology has smallest ‘string length’      non-trivial kinematical dependence

- T. Sjostrand, PS Nucl.Phys.B659(2003)243

## (More Complicated Topologies)

- T. Sjostrand, PS Nucl.Phys.B659(2003)243

## Baryon Number Violation (BNV) in SUSY
Implementation of 2- and 3-body decays in the PYTHIA generator
BNV Colour Topologies
Baryon Number Violation and String Topologies
An explicit detailed model  baryon number flow
Properties and predictions
Summary and Outlook

- Baryon Number Violation (BNV) in SUSY
- Implementation of 2- and 3-body decays in the PYTHIA generator
- BNV Colour Topologies
- Baryon Number Violation and String Topologies
- An explicit detailed model  baryon number flow
- Properties and predictions
- Summary and Outlook

- The Smoking Gun of Baryon Number Violation

## Variation of Fragmentation Assumptions

**PYTHIA model**: essentially stable
- (provided junction Y topology ‘agreed’ upon)

**Central Point ******** Junction baryons are soft, in CM of decay**

**PYTHIA**** vs ****HERWIG**: it matters whether B flow modeled or not
- (HERWIG impl. focussed on perturbative part)

## Slow Baryons @ LHC – How tough to do?

- (simplistic!)

## Slow Baryons @ LHC – How tough to do?

**Not trivial**. But with high cross sections (low masses) may be feasible. Would be **smoking gun of Baryon Number Violation.**
- ILC highly interesting as well. Model applicable to any collider type.

## RPV-SUSY  interesting phenomenology
Esp. BNV has antisymmetric colour structure in interaction term which does not appear in SM (neglecting sphalerons ...)
Detailed model focussing on NP aspects (flow of baryon number) shows new aspects:

Available in the PYTHIA generator (see e,g, PYTHIA 6.4 manual, published last week: JHEP05(2006)026, 582pp )
Not trivial to ‘catch the baryon’ at LHC. Would need detailed study.
Possibilities at ILC also remain to be explored
Though we only applied it to BNV-SUSY, the fragmentation principles are universal, and could easily be used for other BNV physics (so far, we e.g. recycled it for proton remnant fragmentation in min-bias)

- RPV-SUSY  interesting phenomenology
- Esp. BNV has antisymmetric colour structure in interaction term which does not appear in SM (neglecting sphalerons ...)
- Detailed model focussing on NP aspects (flow of baryon number) shows new aspects:
- Available in the PYTHIA generator (see e,g, PYTHIA 6.4 manual, published last week: JHEP05(2006)026, 582pp )
- Not trivial to ‘catch the baryon’ at LHC. Would need detailed study.
- Possibilities at ILC also remain to be explored
- Though we only applied it to BNV-SUSY, the fragmentation principles are universal, and could easily be used for other BNV physics (so far, we e.g. recycled it for proton remnant fragmentation in min-bias)

**Smoking gun of BNV = excess of soft baryons (in CM of decay)**