LHC+LC Synergy: SUSY as a case study

Transcription

1 LHC+LC Synergy: SUSY as a case study εργον συν work together Outline: Why LHC/LC studies? Why SUSY as case study? 5 Examples of Synergy Conclusions Klaus Desch University of Hamburg ALCPG meeting - SLAC 07/01/04

2 Why LHC/LC studies? Learning from experience In the past it was often beneficial for particle physics to have several experimental tools available simultaneously to assess closely related questions. Latest example: LEP+SLC+Tevatron led to many success stories - EW standard model at quantum level -top quark -QCD - prediction of (SM) Higgs mass If we want to formulate a scientific roadmap for particle physics, we must look at the physics potential of future facilities in a coherent fashion. (not only accelerator-based, see cosmic connection; but we should look at the accelerator-based projects in the first place)

3 Why LHC/LC studies? The next big projects in accelerator-based HEP are Tevatron Run2 - running LHC - under construction start: 2007 LC - worldwide consensus: next large accelerator All have their worked out physics case What s left to do?

4 Why LHC/LC studies? The scientific(!) questions to be studied in the LHC/LC group: 0. Compare the physics reach of the machines (this is a preparatory exercise of the real thing, but very helpful still) 1. What will we learn if information from the machines are interpreted simultaneously?? LHC LC 2. Will we learn more (or cover more of the physics space ) if LHC and LC operation will overlap in time? LHC LC

5 LHC/LC study group These questions have started to be investigated in the LHC/LC study group formed in Spring 2002 acknowledged by ICFA Coordinators: R. Godbole, F. Paige, G. Weiglein Collaborative effort of LHC+LC exp. communities and theory/pheno So far 6 WG meetings First (intermediate report) is in final editorial phase Report should be viewed as a first step (contains a lot of comparative studies, but also important work on real synergy questions) More information at

6 LHC/LC study group Structure of the document + editorial contacts: Electroweak Symmetry breaking (weakly) H. Haber, R. Godbole, G. Weiglein, A. deroeck Strong Electroweak Symmetry breaking T. Barklow, K. Mönig Supersymmetric Models KD, K. Kawagoe, M. Nijori, F. Paige, G. Pollesello New Gauge Theories S. Riemann Models with Extra Dimensions J. Hewett Exotics J. Gunion Electroweak and QCD precision tests E. Boos, S. Heinemeyer, J. Stirling, A. deroeck

7 Why SUSY as a case study? Should SUSY be realized, we will have a lot to do! - is it really SUSY? -how is it realized? (particle content) MSSM, NMSSM, -how is it broken? measure as many of the >100 LE parameters as possible measure them as precisely as possible -> extrapolation to high scale Studies so far (naturally) were focused on what the individual machines >can< do alone. Going further needs new way of thinking in the communities (interesting!). can I make it with a little help from my friends??

8 SUSY discovery should be simple at LHC for squark masses < ~2 TeV χ 0 2 q χ 0 1 q Z DISCOVERY SUSY SPECTROSCOPY? require e.g. E miss T >300 GeV and four jets for m(squark) ) = 900 GeV

9 But exclusive reconstruction is really difficult typical SUSY diagram at LHC

10 5 Examples of Synergy: Mass reconstruction of sparticles Reconstruction of Chargino/Neutralino parameters Reconstruction of Stop/Sbottom sector parameters SUSY Higgs sector Telescope to the Planck scale

11 Turning Silver into Gold: Sparticle Masses Gjelsten,Lytken,Miller,Osland,Polesello,Chiorboli,deRoeck,Tricomi TLAS+CMS studies for SUSY point PS 1a: quite favorable point for LHC and LC Nature may be less kind LHC can see gluino, squarks, h,h,a, and most gauginos mass reconstruction difficult at LHC (escaping neutralino + no beam constraints) complicated decay chains

12 Turning Silver into Gold: Sparticle Masses main trick: dilepton edge = endpoint of di-lepton mass spectrum in χ 0 2 χ0 1 l+ l - largest, if χ 0 1 at rest in χ0 2 frame, then m(ll) = m(χ 0 2 )-m(χ0 1 ) m(χ 0 1 ) needed as input!

13 Turning Silver into Gold: Sparticle Masses reconstruction of squark mass: 0 0 m( χ1 ) use p( χ 2) = 1 p( ) and combine with jet momentum m( ) this approach needs the LSP mass as input, therefore the reconstructed squark-, gluino-mass is highly correlated with m(χ 0 1 ):

14 Turning Silver into Gold: Sparticle Masses slepton squark sbottom but even LHC alone can do better:

15 Turning Silver into Gold: Sparticle Masses joint fit of various kinematic edges yields an overconstrained system:

16 Turning Silver into Gold: Sparticle Masses edges only: for 300 fb and LC χ 0 1 mass with 0.2%/1% precision combined with invariant masses: often dominated by LHC energy scale systematics numbers are preliminary

17 Turning Silver into Gold: Sparticle Masses Comments: improvement not so dramatic for SPS1a (already LHC alone quite impressive) this might change a lot for less favorable points (e.g. with large BR(χ 0 2 χ0 1 ττ) ) LC reduces model-dependence significantly (intermediate states seen directly and individually assumed decay chain can be verified!) With the BR s of the lower parts of decay chain known, also couplings (of squarks and gluinos) become accessible (later )

18 Telling the LHC where to look: the χ 0 4 story KD,Kalinowski,Moortgat-Pick,Nojiri,Polesello At the LC, the complete tree-level parameters of the chargino/neutralino system of the MSSM (M 1,M 2,µ,tanβ) can be extracted from mass + (polarized) cross section measurements of the lightest (χ 0 1, χ0 2, χ± 1 ) states. for 100/100 fb -1 LR/RL at 400 and 500 GeV Polarisation 80/60 (e - /e + ) With these parameters all chargino and neutralino masses can be predicted, e.g.: m(χ 0 4 ) = 378.3±8.8 GeV χ 0 4 occurs occasionally also in squark decays leading to another dilepton edge at the LHC:

19 Telling the LHC where to look: the χ 0 4 story 100fb -1 With a special analysis LHC can measure χ 0 4 with m(χ 0 4 ) = 5.5 GeV (or 2.2 GeV if m(χ0 1 ) from LC is taken)

20 Telling the LHC where to look: the χ 0 4 story feeding this mass back into parameter determintation helps:

21 Telling the LHC where to look: the χ 0 4 story Comments: the LC prediction of m(χ 0 4 ) leads to an increase of the LHC statistical sensitivity! (`look elsewhere effect, test of a fixed hypothesis rather than many mass-hypotheses) if it is not seen where predicted, this is important information (MSSM NMSSM or sth. else) this is prototype example where simultaneous running of LHC and LC is very important: suppose, there is a statistically marginal signal seen after the LC prediction call for more luminosity/ improved cuts/trigger etc.

22 Interpreting the production rates: stop/sbottom mixing Hisano,Kawagoe,Nojiri Use combined LHC+LC information to get the stop/sbottom parameters: from LHC edges + LC LSP mass mb m 1 b 2 Ratios of branching ratios of sbottom and stop: 0 0 BR(b) = BR(g bb bb χ ) / BR(g bb bb χ ) BR(t) = BR(edge) / BR(g bbx) weighted M tb = weighted endpoint of g tb χ ± modes ± These observables are measurable at LHC because the χ1 and branching ratios are known from LC! 1 0 χ 2 The set of weak SUSY parameters (M 1,M 2,µ,tanβ) from LC (+LHC) analysis With this set of observables the 5 parameters ( m ) b,m 1 b,m 2 t, θ, 2 b θt can be obtained

23 Interpreting the production rates: stop/sbottom mixing Hisano,Kawagoe,Nojiri Determination of θ b Determination of andm θt t 1 with/without exp systematics

24 SUSY Higgs Synergy KD,E.Gross,S.Heinemeyer,G.Weiglein,L.Zivkovic Indirect prediction of heavy Higgses H/A from light h BR measurements at LC: SUSY Higgs sector depends strongly on stop/sbottom sector green: all SUSY points with LC constraints red: θ b θ t known to 20%/10% from LHC

25 SUSY Higgs Synergy Mass measurement of heavy SUSY Higgs at LHC depends (again) on LSP mass input from LC: H/A χχ 4 + 2χ F.Moortgat

26 (SUSY) Higgs Synergy Dawson,KD,Juste,Rainwater,Reina,Schumacher,Wackeroth LHC is sensitive to top Yukawa coupling of light Higgs through tth production. LC BR measurement (h bb and h WW) turns the rate measurement into an absolute coupling measurement (LC can only do it at high energy (> 800 GeV))

27 Ultimate SUSY Synergy: Learning about SSB Allanach,Grellscheid,Quevedo Discrimination between different SUSY-breaking scenarios Need information from slepton and squark sector! Need percent level accuracy

28 Ultimate SUSY Synergy: Learning about SSB Blair,Martyn,Polesello,Porod,Zerwas Model-independent bottom-up approach: Combined information on Low-Energy SUSY parameters as input to RGE evolution LHC LHC LC

29 Ultimate SUSY Synergy: Learning about SSB Blair,Martyn,Polesello,Porod,Zerwas LHC LHC LC

30 Summary and Conclusions First round of LHC/LC studies almost completed SUSY (as an example for a scenario with very rich new phenomena) greatly benefits from synergy of LHC and LC analyses The studies show in a quantitative manner that joint analyses will improve the knowledge about SUSY (mass measurements, extraction of couplings/mixing angles, extrapolation to higher scales) Some very clear advantages of simultaneous running became clear (hopefully more to come): LC prediction of (possibly marginal) LHC signals (call for higher LHC lumi, improved experimental techniques etc) For me it is hard to imagine that in a SUSY world after LC turn on no new questions to the LHC would appear we always learn iteratively. The LHC/LC study is a very fruitful work together of LHC and LC oriented experimentalists and theorists. We learned a lot. Why don t you join? Special thanks to G.Weiglein + A.de Roeck for their help!