lepton number violating supersymmetryhome.fnal.gov/~skands/slides/dissertation.pdf · ph.d....

Ph.D. DissertationPh.D. Dissertation

PHENOMENOLOGICAL STUDIESON SUPERSYMMETRYAND THE STRONG FORCE

Peter Zeiler SkandsOctober 8, 2004Lund

P. Skands, thesis defense, 8 Oct 2004 – p.1/25

Paper I

Lepton Number Violating Supersymmetry– Decays and First Studies with PYTHIA.

I “Searching for L-Violating Supersymmetry at the LHC”.

By P. Skands.

LU TP 01-32, Oct 2001.

Published in European Physical Journal C23 (2002) 173.


Lepton Number Violating SupersymmetryLepton Number Violating Supersymmetry

General MSSM contains renormalizable Lepton andBaryon Number violating operators.

Proton lifetime bound → either LNV or BNV, not both!(could also be neither ≡ R-parity conservation.)

p

π0

λ′e

+

λ′′



We have considered ∼ 1200 decay processes (1 → 2and 1 → 3) of sparticles to particles, induced at treelevel by the trilinear LNV terms in the superpotential:

WLNV = λijkLiLjEk + λ′ijkLiQjDk + εiLiH2LATER!

Example: fully leptonic χ0 decay:

˜jα

χ0m

`−k

νi

`+j

LNV νi

χ0m

`−k

`+j

νi

LNV ˜kα

χ0m

`+j

νi

`−k

LNV

Matrix Elements implemented in PYTHIA for partialwidth calculations (only SUSY particles and t and bquarks treated as massive).

Initial decay products distributed isotropically in phasespace, ⊕ subjected to QCD and QED bremsstrahlungand (string) hadronization.



We have considered ∼ 1200 decay processes (1 → 2and 1 → 3) of sparticles to particles, induced at treelevel by the trilinear LNV terms in the superpotential:

WLNV = λijkLiLjEk + λ′ijkLiQjDk + εiLiH2LATER!

Matrix Elements implemented in PYTHIA for partialwidth calculations (only SUSY particles and t and bquarks treated as massive).

Initial decay products distributed isotropically in phasespace, ⊕ subjected to QCD and QED bremsstrahlungand (string) hadronization.



Second part: primitive LHC study, based on cuts andneural networks, focussing on experimental triggersand overall discovery potential for LNV-SUSY at LHC.

LLELQDMSSM

mSUGRA P9: Missing ET

SMLLE MODELS

→ Discovery with 30 fb−1 data down to σ = 10−10 mb.


Paper II

Baryon Number Violating Supersymmetry– Hadronization and String Topologies.

II “Baryon Number Violation and String Topologies”.

By T. Sjöstrand and P. Skands.

LU TP 02-46, Dec 2002.

Published in Nuclear Physics B 659 (2003) 243.


Baryon Number Violating SupersymmetryBaryon Number Violating Supersymmetry

This time, ∼ 200 decay channels → PYTHIA.

Again, sometimes they had bothersome expressions...

But all that worked like before.





Γ(χ0 → uidj dk) =1

(2π)31

32M3

χ0

Z

dm2

12

Z

dm2

23 |M(χ0 → uidj dk)|2

|M(χ0 → uidj dk)|2

Nc!λ′′2

ijk

=

2X

α=1

|Q2i−1

αR|2R(u∗

iα, m2

jk)(m2

jk − m2

j − m2

k)“

(a2(u∗

iα) + b2(u∗

iα))(m2

χ0 + m2

i − m2

jk) + 4a(u∗

iα)b(u∗

iα)mimχ0)”

+2

X

α=1

|QjαR

|2R(u∗

jα, m2

ik)(m2

ik − m2

i − m2

k)“

(a2(u∗

jα) + b2(u∗

jα))(m2

χ0 + m2

j − m2

ik) + 4a(u∗

jα)b(u∗

jα)mjmχ0

”

+2

X

α=1

|QkαR|2R(dkα, m2

ij)(m2

ij − m2

i − m2

j )“

(a2(d∗kα) + b2(d∗kα))(m2

χ0 + m2

k − m2

ij) + 4a(d∗kα)b(d∗kα)mkmχ0

”

+2Qi1RQi

2RS(u∗

i1, u∗

i2, m2

jk, m2

jk)(m2

jk − m2

j − m2

k)“

(a(u∗

i1)a(u∗

i2) + b(u∗

i1)b(u∗

i2))(mχ0 + m2

i − m2

ik)

+2(a(u∗

i1)b(u∗

i2) + a(u∗

i2)b(u∗

i1))mimχ0

”

+2Qj1R

Qj2R

S(u∗

j1, u∗

j2, m2

ik, m2

ik)(m2

ik − m2

i − m2

k)“

(a(u∗

j1)a(u∗

j2) + b(u∗

j1)b(u∗

j2))(mχ0 + m2

j − m2

ik)

+2(a(u∗

j1)b(u∗

j2) + a(u∗

j2)b(u∗

j1))mjmχ0

”

+2Qk1RQk

2RS(dk1, dk2, m2

ij , m2

ij)(m2

ij − m2

i − m2

j )“

(a(d∗k1)a(d∗k2

) + b(d∗k1)b(d∗k2

))(mχ0 + m2

k − m2

ij)

+2(a(d∗k1)b(dk2) + a(d∗k2

)b(d∗k1))mkmχ0

”

−22

X

α=1

2X

β=1

QiαRQ

jβR

S(u∗

jβ , u∗

iα, m2

ik, m2

jk)“

mimja(u∗

jβ)a(u∗

iα)“

m2

ik + m2

jk − m2

i − m2

j

”

+mimχ0b(u∗

jβ)a(u∗

iα)“

m2

jk− m2

k− m2

j

”

+ mjmχ0a(u∗

jβ)b(u∗

iα)`

m2

ik− m2

i − m2

k

´

+b(u∗

jβ)b(u∗

iα)“

m2

ikm2

jk− m2

i m2

j − m2

χ0m2

k

””

−22

X

α=1

2X

β=1

QiαRQk

βRS(dkβ , u∗

iα, m2

ij , m2

jk)“

mimka(d∗kβ)a(u∗

iα)“

m2

ij + m2

jk − m2

i − m2

k

”

+mimχ0b(d∗kβ

)a(u∗

iα)“

m2

jk− m2

j − m2

k

”

+ mkmχ0a(d∗kβ

)b(u∗

iα)“

m2

ij − m2

i − m2

j

”

+b(d∗kβ

)b(u∗

iα)“

m2

ijm2

jk− m2

i m2

k− m2

χ0m2

j

””

−22

X

α=1

2X

β=1

QjαR

QkβRS(dkβ , u∗

jα, m2

ij , m2

ik)“

m2

jm2

ka(d∗kβ)a(u∗

jα)`

m2

ij + m2

ik − m2

j − m2

k

´

+mjmχ0b(d∗kβ)a(u∗

jα)`

m2

ik − m2

i − m2

k

´

+ mkmχ0a(d∗kβ)b(u∗

jα)`

m2

ij − m2

j − m2

i

´

+b(d∗kβ)b(u∗

jα)“

m2

ijm2

ik − m2

jm2

k − m2

χ0m2

i

””

Dreiner, Richardson, and Seymour (hep-ph/9912407):







The real challenge was the colour flows!

How do such systems hadronise?


Baryon Number Violating SuSyBaryon Number Violating SuSy

New: 3 (antisym) colour carriers at large momentum sepa-ration – no corresponding (perturbative) coupling in SM!

“Ordinary” string (e.g. Z0 → qq): “Baryonic” string (e.g. ):

q q

q1

q2

q3

junction

B ≡ string topologies w/ junction(s).

10-3

10-2

10-1

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5pCM [GeV]

Np

/ Nπ

n χ decay. Junction protons.n χ decay. Non-junction protons.

qqbar w. ECM = mχ.qqbar w. ECM = 2/3 mχ.

q4

q7

q9q4 q3 q3 qq2 qq2 q1 q1 ui

q7

q6

q6

q5

q5

dj

q9q8

q8

dk


Paper III

The SUSY Les Houches Accord.– Standardising SUSY calculations.

III “SUSY Les Houches Accord: Interfacing SUSY Spectrum Calculators, DecayPackages, and Event Generators”.

By P. Skands, B.C. Allanach, H. Baer, C. Balázs, G. Bélanger, F. Boudjema,A. Djouadi, R. Godbole, J. Guasch, S. Heinemeyer, W. Kilian, J-L. Kneur,S. Kraml, F. Moortgat, S. Moretti, M. Mühlleitner, W. Porod, A. Pukhov,P. Richardson, S. Schumann, P. Slavich, M. Spira, G. Weiglein.

LU TP 03-39, Nov 2003.

Published in Journal of High Energy Physics 07 (2004) 036.


The SUSY Les Houches AccordThe SUSY Les Houches Accord

Problem: lots of people doing SuSy calculations today!Spectrum Calculators: ∼ 7 programs.Relic Density Codes: ∼ 3 programs.Dedicated Decay Packages: ∼ 3 programs.Event Generators: ∼ 10 programs.

And everybody has their own opinion about factors of√2, π, i, counterclockwise or clockwise rotations, pole

or running masses, effective field content, DR or MSregularization/renormalization, field decomposition etc.

This gave rise to some problems...

So why not make an Accord? I.e. agree on a standardset of conventions for SUSY theories, with standard filestructures → unambiguous communication.



At Les Houches 2003, the organisers let me gather alot of experts in a room, to discuss this. I made surenobody could get out for some hours.

Next day, we had another long meeting, and anotherone every day after that, for almost two weeks.

Only a few people got out.

At the end, everybody was tired and agreed.

There followed O(103) mails, and more meetings atCERN, at Montpellier, and latest at Durham.

The result is the SUSY Les Houches Accord, whichnow is implemented in most of the relevant codes.

Now please use it!



At Les Houches 2003, the organisers let me gather alot of experts in a room, to discuss this. I made surenobody could get out for some hours.

Next day, we had another long meeting, and anotherone every day after that, for almost two weeks.Only a few people got out.

At the end, everybody was tired and agreed.

There followed O(103) mails, and more meetings atCERN, at Montpellier, and latest at Durham.

The result is the SUSY Les Houches Accord, whichnow is implemented in most of the relevant codes.

Now please use it!


Paper IV

Bilinear Lepton Number Violating Supersymmetry– Measuring Neutrino Mixing at the LHC?

IV “Measuring Neutrino Mixing angles at LHC”.

By W. Porod and P. Skands.

LU TP 03-50, ZU-TH 20/30, Jan 2004. [hep-ph/0401077]

In Beyond the Standard Model Working Group: Summary report, 3rd LesHouches Workshop: Physics at TeV Colliders, Les Houches, France, 26 May- 6 Jun 2003, B. C. Allanach et al. [hep-ph/0402295].


Bilinear L–violationBilinear L–violation

WSUSY = WMSSM + εiLiH2(Occurs e.g. when R–parity is broken spontaneously)

In context of neutrino masses, the importantconsequences are:

EW symmetry is broken by Higgs and sneutrino vev’s,

〈νi〉 = vi (i.e. m2

W= 1

4g2(v2

d+ v2

u + v2

1+ v2

2+ v2

3)).

Neutrinos mix with neutralinos → 7 × 7 mixing:

In block form: MN =

(

0 m(3×4)

mT(4×3) M (4×4)

)


Measuring a ν angle...Measuring a ν angle...

Mixing depends onΛi = µvi + vdεi

BRPV couplings also responsible for LSP decay.

→ Ratio of χ01 semileptonic branching ratios is strongly

correlated with Λi/Λj !P. Skands, thesis defense, 8 Oct 2004 – p.14/25

Paper V

High Energy Proton Collisions 1– Improving the Description of Underlying

and Minimum Bias Events.

V “Multiple Interactions and the Structure of Beam Remnants”.


LU TP 04-01, Feb 2004.

Published in Journal of High Energy Physics 03 (2004) 053.


High Energy Proton Collisions 1High Energy Proton Collisions 1

The Motivation:

Example: minimum-bias at the Tevatron

Antiproton beam remnant

Proton beam remnant

p

p

g

g


High Energy Proton Collisions 1High Energy Proton Collisions 1

The Motivation:

Real life is more complicated...

Butch Cassidy and the Sundance Kid. Copyright: Twentieth Century Fox Films Inc.


Why Develop a New MI/UE Model?Why Develop a New MI/UE Model?

Need to understand correlations and fluctuations inhadronic collisions. From QCD point of view:many interesting questions remain unanswered.

Any reliable extrapolation to LHC energies will requirea good understanding of the physics mechanisms.Simple parametrizations not sufficient.

Random and systematic fluctuations in the underlyingactivity can impact precision measurements as well asNew Physics searches:more reliable understanding is needed.

Lots of fresh data from Tevatron:→ great topic for phenomenology right now!


Towards a realistic modelTowards a realistic model

p

g

u

s

s

u

d

tohardint.

beamremn.

How are the hard scattering initiators and beamremnant partons correlated?

+ In impact parameter?+ In flavour?+ In longitudinal momentum?+ In colour?+ In (primordial) transverse momentum?


The “intermediate” model:The “intermediate” model:

Dependence on non–trivial transverse density profileof incoming hadrons.

Fully correlated multi-parton densities calculated eventby event, respecting momentum conservation andflavour sum rules, and reducing to standard PDF’s forthe hardest interaction.

Final state multiplicity increased by ISR and FSR, forall interactions. (including correlated PDF’s for ISR.)

Non-vanishing “primordial” k⊥ for shower initiators.

Junction hadronisation (from BNV studies) adapted fordescription of baryon beam remnants.

Colour flow ambiguous at the non–perturbative level.Interesting (and thorny!) issues here, to be continued...


Paper VI

High Energy Proton Collisions 2– Unifying the Description of Radiation and

Interactions.

VI “Transverse-Momentum-Ordered Showers and Interleaved Multiple Interactions”.


LU TP 04-29, Aug 2004.

Submitted to the European Physical Journal C.


Why Develop a New Shower?Why Develop a New Shower?

Incorporate several of the good points of the dipoleformalism within the shower approach

± explore alternative p⊥ definitions+ p⊥ ordering ⇒ coherence inherent+ Merging with Matrix Elements unproblematic.

(unique p2

⊥↔ Q2 mapping; same z)

+ g → qq natural+ kinematics constructed after each branching

(partons explicitly on-shell until they branch)

+ showers can be stopped and restarted at any p⊥ scale⇒ well suited for ME/PS matching

+ allows to combine p⊥ evolutions of showers and multipleinteractions → common (competing) evolution of ISR, FSR, and MI!

≡ ‘Interleaved Multiple Interactions’


Proton Collisions... The New PictureProton Collisions... The New Picture

The building blocks:

p⊥–ordered initial–state parton showers. 4

p⊥–ordered final–state parton showers. 4

p⊥–ordered multiple interactions. 4

p⊥ used as scale in αs and in PDF’s. 4

(Model for) correlated multi–parton densities. 4

Beam remnant hadronization model. 4

Model for initial state colour correlations. (4 — but farfrom perfect!?)

Other phenomena? (e.g. colour reconnections (4), ...)

Realistic tunes to data (not yet!)



The new picture: start at the most inclusive level, 2 → 2 .Add exclusivity progressivelyby evolving everythingdownwards in onecommon sequence:→ Interleaved evolution

(→ also possible to haveinteractions intertwinedby the ISR activity?)

int.number

p⊥

hard int.

1 2 3 4

p⊥max

p⊥min

p⊥1

p⊥2

p⊥3

p⊥23

p⊥4

ISR

ISR

ISR

ISR

p′⊥1

interleavedmult. int.

interleavedmult. int.

interleavedmult int.Intertwined

p2⊥

evolution



The new description represents a new generation interms of detail and sophistication of the physicsdescription of hadron collisions.

But there is still some way to go...

0.3

0.4

0.5

0.6

50 100 150nch

<p⊥>

Tevatron Run II: <p⊥>(nch)

Tune ARapSharp ISRLow FSRHigh FSR


Plans for the futurePlans for the future


Plans for the futurePlans for the future

To work hard!


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