We explore the physics of the general CP-conserving MSSM with Minimal Flavor
Violation, the pMSSM. The 19 soft SUSY breaking parameters are chosen so to
satisfy all existing experimental and theoretical constraints assuming that the
WIMP is the lightest neutralino. We scan this parameter space twice using both
flat and log priors and compare the results which yield similar conclusions.
Constraints from both LEP and the Tevatron play an important role in obtaining
our final model samples. Implications for future TeV-scale $e^+e^-$ linear
colliders(LC) are discussed.Comment: 6 pages, 3 figs. Talk given at LCWS08, Chicago, IL, USA,
  11/16-20/200

Rizzo, Thomas G.

English

arXiv

We explore the physics of the general CP-conserving MSSM with Minimal Flavor Violation, the pMSSM. The 19 soft SUSY breaking parameters are chosen so to satisfy all existing experimental and theoretical constraints assuming that the WIMP is the lightest neutralino. We scan this parameter space twice using both flat and log priors and compare the results which yield similar conclusions. Constraints from both LEP and the Tevatron play an important role in obtaining our final model samples. Implications for future TeV-scale e{sup +}e{sup -} linear colliders (LC) are discussed

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SUSY Without Prejudice at Linear CollidersThomas G. Rizzo ∗SLAC National Accelerator Laboratory2575 Sand Hill Rd., Menlo Park, CA, USAWe explore the physics of the general CP-conserving MSSM with Minimal Flavor Vio-lation, the pMSSM. The 19 soft SUSY breaking parameters are chosen so to satisfy allexisting experimental and theoretical constraints assuming that the WIMP is the light-est neutralino. We scan this parameter space twice using both flat and log priors andcompare the results which yield similar conclusions. Constraints from both LEP andthe Tevatron play an important role in obtaining our final model samples. Implicationsfor future TeV-scale e+e− linear colliders(LC) are discussed.The MSSM with R-parity conservation is the prototypical SUSY model. Although ithas many nice features it is diﬃcult to study in detail as SUSY breaking leads to over120 a priori unknown soft-breaking parameters. The usual approach to this problem inphenomenological studies is to examine only one or a few of the usual SUSY breakingmechanisms, e.g., mSUGRA, GMSB or AMSB which have only a few associated parameters.One may ask whether a study of these models really tells us all we need to know about theMSSM; is there nothing more? How much do we really know about the MSSM?In recent work, we have attempted to go beyond these studies[1] by examining thegeneral CP-conserving MSSM with Minimal Flavor Violation assuming that (i) the ﬁrst 2generations of sfermions are degenerate with negligible Yukawa couplings, (ii) the neutralinois the LSP with the WMAP dark matter constraint used only as an upper bound. This leavesus with only 19 independent, real, SUSY/weak-scale Lagrangian parameters to consider.These include the gaugino masses, M1,2,3, the Higgsino mixing parameter, μ, the ratio of theHiggs vevs, tanβ, the mass of the pseudoscalar Higgs boson, mA, and the 10 squared massesof the sfermions (5 for the assumed degenerate ﬁrst two generations and a separate 5 for thethird generation). Finally, due to the small Yukawa couplings for the ﬁrst two generations,independent A-terms are only phenomenological relevant for the b, t and τ sectors. In theanalysis presented here we will make two independent parameter scans: for the ﬁrst scan of107 parameter points we assume that all of the sfermion mass parameters lie in the range0.1-1 TeV, 1 ≤ tanβ ≤ 50, |Ab,t,τ | ≤ 1 TeV, 43.5 ≤ mA ≤ 1000 GeV, 0.05 ≤ |M1,2, μ| ≤ 1TeV and 0.1 ≤ M3 ≤ 1 TeV. Note the absolute value signs in these quoted ranges as wewill allow the soft-breaking parameters to have arbitrary sign. For this ﬁrst scan, whichgenerates SUSY spartners with light to moderate masses, we will assume ﬂat priors, i.e., weassume that the parameters values are chosen uniformly throughout their allowed ranges.For our second scan, for which will assume a set of log priors for the mass parameters, wewill modify the allowed soft parameter ranges as follows: all the sfermion mass parameterswill be assumed to lie in the range 0.1-3 TeV, 1 ≤ tanβ ≤ 60, 0.01 ≤ |Ab,t,τ | ≤ 3 TeV,43.5 ≤ mA ≤ 3000 GeV, 0.01 ≤ |M1,2, μ| ≤ 3 TeV, and 0.1 ≤ M3 ≤ 3 TeV. This expandedrange will allow us access to both very light as well as heavy sparticle states. Since the goalof this second scan is to make contrasts and comparisons to the ﬁrst, ﬂat prior study, wewill only generate a set of 2 · 106 parameter points to examine in this case.∗Work supported in part by the Department of Energy, Contract DE-AC02-76SF00515LCWS/ILC2008SLAC-PUB-13481December 2008Presented at the International Linear Collider Workshop (LCWS08 And ILC08), 11/16/2008 to 11/20/2008, Chicago , IL, USAOnce the model points are generated we pass them carefully through an extensive listof experimental constraints arising from precision measurements(i.e., Δρ and the invisi-ble width of the Z), ﬂavor physics(i.e., meson-antimeson mixing, b → sγ, B → τν andBs → μ+μ−), the muon g − 2, 5-year WMAP data, direct detection searches(from CDMS,XENON10, DAMA and CREST), as well as Higgs boson and SUSY particle direct searchesat both LEP and the Tevatron[1]. Many of the caveats associated with these collider searches,which are usually ignored, have been included in the present analysis. An example of thisis the search for right-handed sleptons at LEPII; usually, these limits are quoted as being∼ 100 GeV. However, if the mass splitting of the slepton with the LSP, Δm, is suﬃcientlysmall the resulting leptons would be too soft to be observable above SM backgrounds evenin an e+e− environment. Thus, lighter sleptons may actually exist with small values ofΔm that have escaped detection. This eﬀect is indeed shown on the ﬁgures displaying thecombined LEPII limits. A similar eﬀect can also occur for charginos, squarks and gluinosand they, too, may be lighter than is commonly believed if their mass splitting with the LSPis suﬃciently small. Such states do occur in our ﬁnal model samples.It is important to note that the Tevatron plays a very important role at obtaining ourﬁnal model set, in particular searches for stable charged particles, multijets plus missingenergy and trilepton plus missing energy ﬁnal states. These constraints, which we haveanalyzed at the level of fast detector simulations, have not been employed in previous SUSYanalyses. We ﬁnd that only ∼ 68.5(3.0)k models survive this procedure in the case of theﬂat(log) priors.For LC perhaps the most important result of this analysis is the sparticle spectra andwhether or not a given sparticle is kinematically accessible at LC energies. Figs. 1 and 2show this accessibility at collision energies of either 500 GeV and 1 TeV for both sets ofpriors for many possible ﬁnal state spartner pairs. Here, e.g., ‘uLuR’ labels the production ofthe u˜Lu˜∗R + h.c. associated production ﬁnal state. Several things are to be noted from theseﬁgures: (i) The LSP is generally quite light as is χ˜±1 since wino-like and Higgsino-like LSPspectra are the most common in both samples. (ii) The χ˜02 is also often very light as wouldhappen in Higgsino-like scenarios. Note that χ˜±1 (and sometimes χ˜02 as well) is often nearlydegenerate with the LSP leading to long-lived charged particle collider signatures. (iii)Charged sleptons may be accessible in some cases at 500 GeV with the lightest stau beingthe most likely possibility. (iv) There is a reasonable probability that light squarks mayalso be accessible at 500 GeV; this possibility has not been well-studied at LC since it hasgenerally been believed that this possibility is excluded by Tevatron searches. Such searches,however, assume an mSUGRA-like mass spectra which produce large missing energy andmulti-jet ﬁnal states. In the cases we ﬁnd, light squark production fails to pass the requiredTevatron search cuts at signiﬁcant rates to be detected, evading such searches. (v) There isa reasonable probability that a light Higgs exists with a mass below the LEPII SM Higgsbound of 114 GeV due to a reduced ZZh coupling and/or the possibility that h → 2χ˜01 isallowed with a signiﬁcant rate. The former generally occurs in the ‘non-decoupling’ regionwhen MA is relatively small. These possibilities has not been well explored within the pureMSSM context.The next most important result for LC is the nature of the nLSP. Fig. 3 shows thatwhile χ˜±1 and χ˜02 are seen to be the most likely nLSP candidates we ﬁnd that almost anyother sparticle can play this role with a probability on the order of a few percent for eitherchoice of prior. Note that light right-handed squarks may be the nLSP in some cases; if thecorresponding mass splitting with the LSP is small, e.g., less than a few GeV, these squarksLCWS/ILC2008Presented at the International Linear Collider Workshop (LCWS08 And ILC08), 11/16/2008 to 11/20/2008, Chicago , IL, USAFigure 1: Fraction of the full model sample with kinematically accessibility of SUSY partnersat a 500 GeV and a 1 TeV LC assuming ﬂat priors.LCWS/ILC2008Presented at the International Linear Collider Workshop (LCWS08 And ILC08), 11/16/2008 to 11/20/2008, Chicago , IL, USAFigure 2: Same as the previous ﬁgure but now for log priors.LCWS/ILC2008Presented at the International Linear Collider Workshop (LCWS08 And ILC08), 11/16/2008 to 11/20/2008, Chicago , IL, USAFigure 3: Identity of the nLSP in the case of ﬂat(top) and log(bottom) priors.LCWS/ILC2008Presented at the International Linear Collider Workshop (LCWS08 And ILC08), 11/16/2008 to 11/20/2008, Chicago , IL, USAwill be very diﬃcult to observe at the LHC and even at LC due to large γγ backgrounds. Wecan see this explicitly in Fig. 4 which shows the nLSP-LSP mass splitting for the diﬀerentnLSP possibilities for the case of log priors. With charginos playing the nLSP role we seethe nLSP-LSP mass splitting can be particularly small and that most of the light charginomodels in this case are removed by the Tevatron stable particle search as can be seen in thelower left-hand side of the ﬁgure.Figure 4: LSP-nLSP mass splitting as a function of the LSP mass showing the nLSP identityin the case of log priors.From this study it is clear that the MSSM can be much more complex than one wouldimagine by examining speciﬁc SUSY-breaking scenarios. If SUSY is discovered at the LHCit is quite clear that a LC will be needed in order for us to get a true picture of the underlyingphysics.References[1] For full analysis details and original references, see C. F. Berger, J. S. Gainer, J. L. Hewett andT. G. Rizzo, arXiv:0812.0980 [hep-ph].LCWS/ILC2008Presented at the International Linear Collider Workshop (LCWS08 And ILC08), 11/16/2008 to 11/20/2008, Chicago , IL, USA

SUSY Without Prejudice at Linear Colliders

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SUSY Without Prejudice at Linear Colliders

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