Recently we examined a large number of points in a 19-dimensional parameter
subspace of the CP-conserving MSSM with Minimal Flavor Violation. We determined
whether each of these points satisfied existing theoretical, experimental, and
observational constraints. Here we discuss the properties of the parameter
space points allowed by existing data that are relevant for dark matter
searches.Comment: 4 pages, 3 figs; talk given at SUSY0

Gainer, James S.

English

arXiv

Recently we examined a large number of points in a 19-dimensional parameter subspace of the CP-conserving MSSM with Minimal Flavor Violation. We determined whether each of these points satisfied existing theoretical, experimental, and observational constraints. Here we discuss the properties of the parameter space points allowed by existing data that are relevant for dark matter searches

UNT (University of North Texas) Digital Library

Work supported in part by US Department of Energy contract DE-AC02-76SF00515.SLAC-PUB-13799MSSM Dark Matter Without PrejudiceJames S. Gainer1SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, CA, 94025, USAAbstract. Recently we examined a large number of points in a 19-dimensional parameter subspaceof the CP-conserving MSSM with Minimal Flavor Violation. We determined whether each of thesepoints satisfied existing theoretical, experimental, and observational constraints. Here we discuss theproperties of the parameter space points allowed by existing data that are relevant for dark mattersearches.Keywords: pMSSM, general MSSM phenomenology, dark matterPACS: 11.30Pb,12.60.Jv,14.80.Ly,95.35.+dINTRODUCTIONThe MSSM has a large parameter space; this raises the question of how well weknow its properties aside from specific SUSY breaking scenarios such as mSUGRA,AMSB, GMSB, etc. In an attempt to address this question, we performed scans ofa 19-dimensional subspace of the full 100+ parameter (R-parity conserving) MSSM(sometimes referred to as the “phenomenological MSSM”) and applied a comprehen-sive set of theoretical, experimental, and observational constraints, thereby obtaining alarge set of “models” (parameter space points) which are consistent with existing data[1].The particulars of and results from this scan are discussed in other presentations at thisconference[2, 3]. Here we will be concerned with the implications of this scan for darkmatter, addressing the properties of LSPs in the set of allowed MSSM models generated,and in particular their signatures in direct detection and indirect detection experiments.PROPERTIES OF THE LSPA histogram of the masses of the four neutralino species in the model set is shown inFigure 1. In all models in this set, the lightest neutralino is the LSP.It is also notable that most LSPs are relatively pure eigenstates, with models where theLSP is Higgsino or mostly Higgsino being by far the most common. A precise descrip-tion of the content of LSPs in the model set is presented in Table 1. The prevalence ofnearly pure eigenstates is not surprising; one would expect the LSP be a pure eigenstate1 Present addresses: Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208High Energy Physics Division, Argonne National Laboratory, Argonne, IL 604390 200 400 600 800 10000500100015002000250030003500400045005000550060006500700075008000    number of modelsm  [GeV]FIGURE 1. The distribution of neutralino masses for models in the model set.TABLE 1. The fractions of models in the model set for whichthe LSP is of each of the given types. These types are defined interms of the modulus squared of elements of neutralino mixingmatrix in the SLHA convention.LSP Type Definition Fractionof ModelsBino |Z11|2 > 0.95 0.14Mostly Bino 0.8 < |Z11|2 ≤ 0.95 0.03Wino |Z12|2 > 0.95 0.14Mostly Wino 0.8 < |Z12|2 ≤ 0.95 0.09Higgsino |Z13|2 + |Z14|2 > 0.95 0.32Mostly Higgsino 0.8 < |Z13|2 + |Z14|2 ≤ 0.95 0.12All other models 0.15fairly often in a random scan of Lagrangian parameters such as t at performed. As thedifferences betweenM1,M2, andµ will often be large compared toMZ, the eigenstatesof the resulting mixing matrix will be essentially pure gaugino and Higgsino states.RELIC DENSITYIn applying constraints to models, we did not demand that theLSP, in any given model,account for all of the dark matter; we required only that the (t rmal) LSP relic densitynot be too large to be consistent with WMAP. The distributionof Ωh2|LSP values inour model set is shown in the left panel of Figure 2. It is interesting to note that thisdistribution is peaked at small values ofΩh2|LSP and that the range of possible values ofΩh2|LSP is found to be much larger than those obtained by analyses of specific SUSYbreaking scenarios.The distribution of predictions forΩh2|LSP as a function of the LSP mass for modelsin the model set is shown in the right panel of Figure 2. We see from this figure thatΩh2|LSP generally increases with the LSP mass. However, a large range of values forthe relic density are possible at any given LSP mass. The empty region in Figure 2whereΩh2|LSP≈ 0.001−0.1 andmLSP≈ 50−100 is due to the paucity of models withHiggsino or Wino LSPs in this mass range (as such models wouldgenerally have achargino light enough for discovery at LEP) together with the fact that in general, LSPswhich are mostly Higgsino or Wino give lower values ofΩh2|LSP. 0 500 1000 1500 2000 0.001  0.01  0.1modelsΩ h2Number of Models with Relic Density in Given Range 1e-06 1e-05 0.0001 0.001 0.01 0.1 0  100  200  300  400  500  600  700  800Ω h2mLSP [GeV]LSP Mass Versus Relic DensityFIGURE 2. The left panel shows the distribution ofΩh2|LSP for models in the model set. The rightpanel shows the values ofΩh2|LSP versus LSP mass for models in the model set.DIRECT DETECTION OF DARK MATTERTo implement constraints on MSSM parameter space resultingfrom direct WIMP de-tection experiments and to study the direct detection signature of allowed models, wecalculated the spin-dependent and spin-independent WIMP-nucleon cross sections us-ing micrOMEGAs 2.21. The quantity actually measured in experim nts is the WIMP-nucleon cross section scaled to the fraction of the dark matter density representedby the LSP, hence the cross section data presented in the figurbelow are scaled byξ = Ωh2|LSP/Ωh2|WMAP. These experiments generally provide a more significant boundon the spin-independent WIMP-nucleon cross sections, and he ce we will focus onthese.In the left panel of Figure 3, the distribution for the scaledWIMP-proton spin-independent cross section versus relic density for our model sample is presented. Per-haps not surprisingly, larger values of the cross section are generally found at largervalues ofΩh2|LSP. However, we note that even for relic densities close to the WMAPvalue, where there is little contribution to the diversity in scaled cross section from vari-ation in the relic density,ξ σp,SI is seen to vary by almost eight orders of magnitude.In the right panel of Figure 3, we see the scaled WIMP-proton spi -dependent andspin-independent cross sections as a function of the LSP mass, together with the con-straints from XENON10 and CDMS. To take into account significant theoretical uncer-tainties in the calculation of the WIMP-proton cross section, we allowed for a factor of4 uncertainty in the calculation of the WIMP-nucleon cross section. Here as well, therange in the value of the scaled WIMP-nucleon cross section is notable. 1e-18 1e-16 1e-14 1e-12 1e-10 1e-08 1e-06 0.0001 100ξσSI,p [pb]mLSP [GeV]LSP Mass Versus WIMP-Proton σSIModelsCDMSXenon 10FIGURE 3. The left panel shows the distribution of scaled WIMP-protonspin-independent crosssection versus the LSP contribution to relic density for models in the model set, while the right handpanel shows the values of scaled WIMP-proton spin-dependent cross versus LSP mass for models in themodel set. In the right panel, the CDMS and Xenon10 bounds, which provide the strongest limits for therange in LSP mass relevant for these models, are shown.Indirect Detection of Dark MatterThe PAMELA collaboration has recently claimed an excess in the ratio of cosmic raypositrons to electrons observed at energies above 10 GeV. Anattempt to quantify theextent to which these results, together with various other observations including thoseof the Fermi-LAT, may be understood in terms of LSP annihilation in SUSY models inthe model set described here is ongoing; some early results have been presented[4].ACKNOWLEDGMENTSWork supported in part by the Department of Energy, ContractDE-AC02-76SF00515.REFERENCES1. For details of the model scan, original references and further results, see C. F. Berger, J. S. Gainer,J. L. Hewett and T. G. Rizzo, JHEP0902, 023 (2009) [arXiv:0812.0980 [hep-ph]].2. The procedure by which this model set was generated is alsodescribed in more detail in the presenta-tion by T. G. Rizzo: arXiv:0907.1668 [hep-ph].3. For discussions of the implications of these results to LHC searches, see the presentation by J. Conley.4. A more in depth discussion of the implications of our pMSSMscan for dark matter searches, withoriginal references and further results is found in R. C. Cotta, J. S. Gainer, J. L. Hewett and T. G. Rizzo,arXiv:0903.4409 [hep-ph], which will be appearing in the NJP focus issue, ’Dark Matter and ParticlePhysics’.

MSSM Dark Matter Without Prejudice

Abstract

Similar works

Full text

Available Versions

UNT (University of North Texas) Digital Library