Determination of SUSY Parameters at LHC/ILC Hans-Ulrich Martyn RWTH Aachen & DESY.
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Transcript of Determination of SUSY Parameters at LHC/ILC Hans-Ulrich Martyn RWTH Aachen & DESY.
Determination of SUSY Parameters at LHC/ILC
Hans-Ulrich MartynRWTH Aachen & DESY
H-U Martyn SUSY parameter determination at LHC/ILC 2
Outline
• Why and how to explore supersymmetry
• Discovery and measurements at LHC
• Precision measurements at ILC
• Reconstructing supersymmetry
• Dark matter and colliders
• Scenarios off mainstream
• Summary and outlook
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Why supersymmetry
Most attractive extension of Standard Model
• ensures naturalness of hierarchy scales
• unification of fundamental gauge forces
• provides cold dark matter candidate
• stabilisation of light Higgs mass corrections
• local SUSY incorporates gravity
• additional sources of CP violation
• maximal symmetry of fermions & bosons
EW data consistent with weak-scale SUSY
LHC experimentsoutcome extremely important, huge impact on
futureprojects - ILC, VLHC, superB, super… discovery - revolution in particle physics
Ellis et al 06
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MSSM
• Building blocks SM MSSM– duplication of particles sparticles
– 105 new parameters in MSSM R-parity conserving
• Biggest mystery - symmetry breaking invoke hidden sector
• Plethora of mediation mechanisms:gravity, gauge, gaugino, anomaly, string inspired, … reduced set of parameters– what are dominant effects producing couplings of hidden sector
and MSSM fields: tree-level, loop-induced, ..., ?
Hidden sector MSSM sectorFlavour blind
mediators
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Soft parameters
GUT scale low scale MSSM Observables
mSUGRA:m0, m1/2, A,tanβ, sign
string inspired models
GMSB
AMSB
…..
masses, decay widths,spin, couplings, mixings,quantum numbers,cross-sections
RPV, CPV, LFV …
neutralinos/charginossleptonssquarksHiggs (h,H,A)
, tanβ, Af
at present
RGEMGUT, MX, MS, HO corrections, renormalisation scheme..., ?
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Soft parameters
GUT scale low scale MSSM Observables
mSUGRA:m0, m1/2, A,tanβ, sign
string inspired models
GMSB
AMSB
…..
masses, decay widths,spin, couplings, mixings,quantum numbers,cross-sections
RPV, CPV, LFV …
neutralinos/charginossleptonssquarksHiggs (h,H,A)
, tanβ, Af
in future
all obstacles solvable with sufficient precision data -- need new techniques at hadron colliders
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Experimental facilities
LHC
• 2007 commissioning @ 0.9 TeV
• 2008 start operation @ 14 TeVgoal: few fb-1 per experiment
• 2010 reliable results on new physics, discoveries?
• huge discovery potential up to scales of m ~ 2.5 TeV
ILC
• 2006 reference design
• 2009 technical design
• 2010 + … ready for decision
• 7 - 8 years construction
• polarised e+e-, e-e-, γγ
• high-precision measurements up to kinematic limit 0.5 - 1 TeV
pp 14 TeV e+e- 1 TeV
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Exploring supersymmetry LHC
Dominant production of strongly interacting squarks, gluinos Many states produced at once,
long decay chains complicated
final states
ILCProduction of non-colored
sleptons,neutralinos, charginosSelect exclusive reactions,
bottom-upapproach, model independent
analysis
Considerable synergy between LHC and ILC
combined analyses, concurrent running
SPS 1a’ mSUGRA benchmark
favourable for LHC & ILC
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Discovering SUSY at LHC
• Signatures from gluino/squark decay chain: high pT multi-jets, isolated leptons,
large missing energy
• Inclusive search Meff=∑1,4ETi + ET
miss
QCD background reliably calculable?
W, Z, tt production Anastasiou
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Early discovery of SUSY at LHC?• Is there New Physics?
What is the scale?
Science community expects fast and reliableanswers, e.g. planning for future facilities
• Understanding detector and ETmisss
spectrum crucial!
• Discovery potential vs luminosity
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Reconstructing masses at LHC
Exploit variety of invariant mass distributions, low & high end pointsConstruct kinematic constraints on sparticle masses precise mass differences seriously limited by poor neutralino mass
Nojiri, SUSY06
strong slR - χ1 correlation
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Reconstructing masses at LHC
• End point method: waste of statistics and information
• Mass relation method: exact kinematics using complete events
• bbll channel– 5 masses: each event define 4-dim hypersurface in 5-dim mass space
– 5 events sufficient to solve mass equations
– many events: overconstraint fit, solve for masses, improved resolution
• All sparticle masses known: reconstruction LSP momentum
Kawagoe, Nojiri, Polesello 2004
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Spin, L/R sfermion?• Shape of decay distribution carry spin information
• Problems: pick up correct combinationquark + near lepton, tell ql+ from anti-ql+
• Solution: lepton charge asymmetry
• Assumptions: more squarks than antisquarkssquarks/sleptons dominantly left or right neutralino spin ½
• Distinct from other models, e.g. UED
spinless
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Finding sparticles with help of ILC
• Light neutralinos and chargino found at ILC
Prediction of masses of heavy neutralinos and charginomay not be accessible at ILC
• New particle can be identified at LHC via‘edge’ in the di-lepton mass spectrum
~0
4
~0
2
LHC/ILC interplay: Phys.Rept.426 (2006) 47
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SPS 1a’ spectrum from LHC
LHC analysis
• access to high mass states, sleptons and gauginos via cascades
• resolution limited by strong correlations with neutralino LSP
• mass differences much more accurate
Correct interpretation?
neutralino
sneutrino
KK photonAguilar-Saavedra et al
2006
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Masses at ILC
• Energy spectrum, end points
δm ~ 0.1 GeV
• Threshold excitation curvecharacteristic β dependence, steep rise
δm ~ 0.05 - 0.2 GeV
flat energy spectrum
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Masses -stau
Stau production
flat energy spectrum distorted to triangular shapefit upper end point mstau
• Coannihilation regionsmall Δm = mstau-mχ 3 GeV accessible
difficult measurement due to huge γγ bkgimportant to get DM constraint
very problematic for LHC
mstau = 173 GeV
δm ~ 0.3 GeV
Point D’
mstau = 218 GeV
Δm = 5 GeV
δm ~ 0.15 GeV h-um
04
E+E-
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Masses - gauginos
Neutralino production
Chargino production
Many reactions to get the mass of the lightestneutralino very accurately! δm ~ 0.05
GeV
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Masses - cascade decays
Decay chains à la LHC
kinematics of cascade decay provides access to intermediate slepton2-fold ambiguity for mass solutions
extremely narrow mass peak δm/m ~ 5∙10-5
Similarly: selectron reconstruction
Berggren 05
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Masses & mixings
Chargino sector
Mass matrix
masses from threshold excitation
Mixings
polarised cross sections σL,R[11] and σL,R[12]
disentangle ambiguities and determinemixing angles cos 2ΦLRChoi et al
2000
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Masses & mixings
Stop production
lightest squark in many scenarios, difficult todetect at LHC
Mixing
polarised cross sections
Minimal mass reconstructed from kinematics, momentumcorrelations, using mχ
peak at mstop Finch et al 04
SPS 5
Bartl et al 97
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Spin
Threshold productionand
Angular distribution
all masses known: reconstructionpolar angle Θ (2-fold ambiguity)
Unambiguous spin assignmentmodel inependent, distinct from e.g. UED
L/R quantum numbers via polarisationR sfermions prefer right-handed electrons e-
R
L sfermions prefer left-handed electrons e-L
Choi et al 2006
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Couplings
Basic element of SUSYidentical gauge and Yukawa
couplingsSU(2) gauge g = Yukawa ĝ U(1) gauge g’ = Yukawa ĝ’
Slepton production
Freitas et al, 04
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SPS 1a’ spectrum from LHC+ILC
Coherent LHC+ILC analysis
• complementaryspectrum completed
• superior to sum of individual analyses
• accuracy increased by 1-2 orders of magnitude
Challenge:experimental accuracy matched by theory?
Aguilar-Saavedra et al 2006
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How to proceed?
• We want to understand the relation between the visible sector, observables, and the fundamental theory
SUSY provides a predictive framework
• How precise can we predict masses, x-sections, branching ratios, couplings, … ?– many relations between sparticle masses at tree-level, much worse at loop-level
– choice of renormalisation scheme?
• Which precision can be achieved on parameters of the MSSM Lagrangian?
– Lagrangian parameters not directly measurable
– parameters not always directly related to a particular observable, e.g. µ,tan ß
– fitting procedure, …
• Can we reconsruct the fundamental theory at high scale?
– unification of couplings, soft masses, … ?
– which SUSY breaking mechanism, origin of SUSY breaking?
Goals of the SPA Project
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SPA convention and project
• Supersymmetry Parameter AnalysisSupported by ~100 theorists & experimentalists
• SPA Convention
renormalisation schemes / LE parameters / observables
• Program repository
theor. & expt. analyses / LHC+ILC tools / Susy Les Houches Accord
scheme translation, RGE & spectrum calculators, event generators, fitting, …
• Theoretical and experimental tasks
short- and long-term sub-projects, SUSY calc. vs expt., LO NLO NNLO, …, new channels & observables, combine LHC+ILC data
• Reference point SPS 1a’
derivative of SPS 1a, consistent with all LE and cosmological data • Future developments
CP-MSSM, NMSSM, RpV, effective string theory, etc.
You are invited to join! http://spa.desy.de/spa/ EPJC 46 (2006) 43
Hollik, Robens
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Extracting Lagrange parameters
Global fit of all available ‘data’ to most up-to-date HO calculationsinput: masses, edges, x-sects, BRs from LHC & ILC
~120 values incl. realistic error correlationstheory: no errors (no reliable estimate available)
output: ~20 parameters
tools Fittino (Bechtle, Desch, Wienemann), SFitter (Lafaye, Plehn, D. Zerwas)
Results SPS 1a’ high precision
LHC alone not able to constrain
most parameters Arkani-Hamed
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High-scale extrapolation
• Gauge couplings α-1
grand unification ~2σ / giU~2% ε3 at ~8σ level
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High-scale extrapolation
• Universality of gaugino & scalar mass parameters in mSUGRA
• Evolution in GMSB distinctly different from mSUGRA
• Bottom-up evolution of Lagrange parameters provides high sensitivity to SUSY breaking schemes
Q [GeV] Q [GeV]
1/Mi[GeV-1] Mj2 [103 GeV2]
mSUGRA
Q [GeV]
Mj2 [103 GeV2]
GMSB
MM
Porod
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Testing mSUGRA
mSUGRA fit excellentUniversality can be tested in bottom-up approach
non-coloured sector at permil to percent levelcolored sector needs improvement
LHC+ILC: Telescope to Planck scale physics
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metastable stau
Dark matter & colliders
Cold dark matter in Universe ΩDM≈ 22%
ΩDMh2 = 0.105 ± 0.008 WMAP
Understanding nature of cold dark matter requires
• direct detection DM particle in astrophysical expt
• precise measurement of DM particle mass & spin at colliders
• compare relic density calculation with observation Ωχ h2~ 3 ∙10-27cm3s-1/<σv>
requires typical weak interaction annihilation cross section
Candidates: neutralino, gravitino, sneutrino, axino, …Formation: freeze out of thermal equilibrium
in general Ωχ » 0.2, annihilation mechanism needed
thermal production
late decays Kraml, Allanach
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Neutralino dark matter
SPS 1a’ ‘bulk region’
annihilation through slepton exchange
χχ тт, bbσχχ depends on light slepton masses & couplings
LHC: precision ~20% (very high lumi)
assuming mSUGRA, ‘a posteriori’ estimate/fix of unconstrained parameters, e.g. mixings
LHC + ILC: precision ~1-2%
matches WMAP/Planck expts Reliable prediction for direct neutralino -
proton detection cross section
Baltz 06
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Neutralino dark matter
LCC2 ‘focus point region’
heavy sfermions, light gauginos
annihilation ΧΧ WW, ZZ
σχχ depends on M1, M2, μ, tanβ
LHC: study gluino decays, not enough constraints to solve neutralino matrix
LHC + ILC: ~10% precision on relic abundance
ILCresolves
LHC multiple solutions
bino
wino
Higgsino
M1
μ
parasitic LHC peak at Ωχ ~ 0
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Gravitino dark matterGravitino mass set by SUSY breaking scale F of mediating
interaction m3/2 =F/√3∙MP Planck scale MP =2.4∙1018 GeV
In general free parameter depending on scenariosupergravity, gaugino, gauge mediationm3/2 = TeV … eV
Most interesting: gravitino LSP, stau NLSP m3/2 = few GeV - few 100 GeV
Dominant decay gravitational coupling, lifetime sec - years
Gravitino not detectable in astrophysical expts
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Gravitino dark matter
Detecting metastable staus & gravitinosidentify & record stopping stau stau mass
wait until decay stau lifetimemeasure τ recoil spectra gravitino mass
rare radiative decays gravitino spin γ- τ correlations in
LHC detectors not appropriate stau mass ok, no lifetime or decay spectramoderate rate, high background, busy timing
external absorber/calorimeter needed
ILC ideal environmenthigh rate, adjustable via cms energy
low duty cycle ~0.5%, excellent calorimetry
Hamaguchi et al 04, Feng, Smith 04, DeRoeck et al 05, H-UM 06
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trap
Gravitino dark matter GDM ε scenario mo=m3/2=20 GeV, M1/2=440 GeV
ILC case study L=100 fb-1 @ 500 GeV (<1 year data taking)
• Prolific stau production
• Lifetime measurement
• Decay spectrum
Access to Planck scale / Newton’s constant
• SUSY breaking scale
• Unique test of supergravity:gravitino = superpartner of graviton
H-U M, EPJC 48 (2006) 15
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Off mainstream scenarios
• Scenario SPS 1a’ is just a benchmark, a test bed
• Nature may be very different from SPS 1a’, mSUGRA, or …
• Other possibilities– complex parameters, CP phases baryogenesis
– lepton flavour violation neutrino masses
– R-parity violation unstable LSP, neutrino masses
– alternative SUSY breaking mediation anomaly, gauge, gaugino, …
mixed scenarios of SUSY breaking
– additional matter/gauge fields NMSSM, UMSSM, ESSM, …
– additional dimensions
– split SUSY
– and many more …
• Different signatures at LHC / ILC
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CP phases
CPV in SUSY may explain baryon asymmetryCP phases
affect CP-even quantities
generate CP-odd observables (triple products)
EDM constraints for 1st, 2nd generation sfermionsand charginos/neutralinos mSUGRA Φμ < 0.1-0.2
Stop decay widths μ, At
strong phase dependence Φ(At) of stop chargino + b
Neutralino sector in selectron production μ, M1
pure Χi0 exchange in t and u channel
transversely polarised e-e- beams
cross section CP even
azimuthal asymmetry CP odd pse_L∙(se1x se2)
complementary to
SPS 1a
S/√L
Bartl et al
Kernreiter, Rolbiecki
2 σ @ L=100 fb-
1
m=380 GeV
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Lepton Flavour Violation
LFV in slepton pair production
Seesaw mechanism to generate neutrino masses mν
LR extension: νR singlet fields and superpartners
added to MSSMsensitivity σLFV ~ 0.1-1 fb
Majorana mass scale MR~1013-1014 GeV
radiative decay Br(μeγ)~10-13
Massive neutrinos affect RGEs of sleptonsflavour off-diagonal terms with large Yukawacouplings for 3rd generationkink in evolution of L3, H2
M(νR3) = (5.9±1.6) 1014 GeV
μe τμ
SPS 1a
Deppisch et al 04
Blair et al 05
Deppisch
SPS 1a’
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Split SUSY
SUSY breaking scale split between scalar & gaugino sectors
Spectrumlight Higgs, neutralinos, charginos, gluino squarks, sleptons, H, A extremely heavy
Signatures strongly dependent on gluino lifetime
long-lived gluino, R-hadrons LHCdisplaced vertices
stable R0 missing ET
stable R+ balanced pT
Chargino/neutralino sector LHC & ILCconventional phenomenology for searches/massesanomalous Yukawa couplings from gaugino-Higgsino mixing
Both LHC & ILC needed to establish SUSY Lagrangianat common scalar mass scale m˜
Arkani-Hamed, Dimopoulos
Kilian et al 04
Provenza
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Summary & outlook
Experiments at LHC will tell if weak-scale supersymmetry isrealised in nature
Methods and techniques have been developed to discover andexplore supersymmetry. Close contacts between experiment andtheory are needed to go beyond basic discovery
SPA project provides a platform for discussions
Both accelerators, the LHC and a future ILC, are necessary tounderstand the sparticle spectrum in detail and to unravel in amodel-independent way the fundamental supersymmetry theory
High-precision measurements of low-energy Lagrange parameters
offer the unique possibility to perform reliable extrapolationstowards the GUT / Planck scale and to test the concepts ofunification of the laws of physics