Non-Universal Gaugino Masses, CDMS, and the LHC

0.17 MB·

by  Michael Holmes

Non-Universal Gaugino Masses, CDMS, and the LHC
Michael Holmes and Brent D. Nelson
Department of Physics, Northeastern University, Boston, MA 02130, USA
(Dated: January 8, 2010)
We consider thepossibility that therecently reported eventsat theCDMS-II direct dark matter
detection experiment are the result of coherent scattering of supersymmetric neutralinos. In such
a scenario we argue that non-universal soft supersymmetry breaking gaugino masses are favored
with aresulting lightest neutralino with significant Higgsino andwino components. Wediscuss the
accompanyingsignalswhichmustbeseenatliquid-xenondirectdetectionexperimentsandindirect
detection experiments if such a supersymmetric interpretation is to be maintained. We illustrate
the possible consequences for early discovery channels at the LHC via a set of benchmark points
0
designed togive rise to an observed eventrate comparable to thereported CDMS-II data.
1
0
2
Introduction. It has been widely held for some time of a supersymmetric neutralino from the germanium

n thatoneofthemostattractivevirtuesofsupersymmetry components in the CDMS detector a number of very
a
as a theory relevant at the electroweak scale is the pos- exciting corollaries may follow. The implications of
J
sible presence of a stable, massive, neutral state in the these events has already been studied in a number of
8
superpartner spectrum capable of explaining the miss- interesting model contexts [6, 7, 8, 9]. In this work

] ing non-baryonic matter in the cosmos [1]. An excellent we will outline some of the possible implications of the
h
candidateforthisdarkmatterparticleisthelightestneu- CDMS data on the nature of supersymmetric models
p
tralinoofsupersymmetry[2,3]. Thediagramswhichgive generally. To illustrate these features we will consider
-
p rise to annihilation among relic neutralinos are among a number of benchmark points – all of which could
e
the same diagrams which determine the interaction rate generate signals of the sort reported by the CDMS
h
of relic neutralinos in our local halo with terrestrial de- experiment. One of the most important conclusions is
[
tectors. Therefore, supersymmetric models whose light- that some amount of non-universality in the gaugino

2
est supersymmetric particle (LSP) has the appropriate soft supersymmetry-breaking masses may need to be
v
properties to account for the needed non-baryonic dark present. We will discuss the crucial cross-checks and
7
0 matter are often also models which could give rise to an corroborating observations that must be seen in the
5 observablesignalindirectdetectionexperiments. Estab- next round of data-taking in both germanium- and
4 lishing the existence of sucha dark matter candidate via xenon-based detectors for these conclusions to hold. We
.
2 theobservationofelasticscatteringofthestateoffoftar- will alsoconsider the prospects for indirect detection via
1 getnucleihasbeenthepursuitofavarietyofexperiments the observation of the decay products from neutralino
9 for some period of time [4]. pair-annihilation at gamma-ray observatories and the
0
Recently, the CDMS-II collaborationhas reported the neutrino observatory at IceCube. We will comment on
:
v observation of 2 nuclear recoil events consistent with the compatibility of any supersymmetric interpretation
Xi the scattering of a weakly-interacting massive particle of the CDMS data with recent measurements of cosmic
(WIMP) from germanium nuclei in a total exposure of anti-matter fluxes from the PAMELA experiment and
r
a 612 kg-days [5]. The measured recoil energies for these with thermal calculations of the relic density of stable
two events were 12.3 keV and 15.5 keV, near the low neutralinos. Finally, we will briefly comment on what
end of the recoil energies considered. In this energy we may expect from the LHC at center-of-mass energies
range the CDMS collaboration estimates their signal ef- of 7, 10 and 14 TeV for our candidate models.
ficiency to be no less than 25%, reaching a maximum
of 32% at 20 keV recoil energies. The expected number
Direct Detection of Neutralino Recoils in Germanium.
of background events from mis-identified electron scat-
tering events or neutron scattering events generated by We beginwiththe methodologyemployedtotranslate
radioactive decays and/or cosmic ray events was esti- the parameters of supersymmetric models into predic-
mated to be ∆N = 0.6 0.1(stat) prior to unblind- tions of event rates at the CDMS-II in a given amount
±
ing. This estimate was subsequently estimated to be of exposure (fiducial volume time of data collection).
×
∆N =0.8 0.1(stat) 0.2(syst) after investigating the To compute the interactionrate ofrelic neutralinos with
± ±
signal events in greater detail. It is therefore quite pos- the nucleiofthe targetmaterialoneconsidersbothspin-
sible that these events are simply mis-identified back- dependent (SD) and spin-independent (SI) interactions.
ground events. Taken as a signal they imply a coherent Fortargetnucleiwithlargeatomicnumbersthe SIinter-
scattering cross-section for a WIMP in the local halo at action,whichiscoherentacrossallofthenucleonsinthe
roughly the few 10−44 cm2 level. nucleus, tends to dominate. The SI cross section σSI is
×
If these events are interpreted as the scattering computedinDarkSUSY[10]onanarbitrarynucleartarget
2
via The sensitivity of the CDMS-II experiment, when
translated into the size of the SI cross section σSI, is
µ2 χp
σSI = iχ ZGp+(A Z)Gn 2, (1) dependent on the mass of the LSP neutralino. For LSP
where i labelχsithe nπuc(cid:12)(cid:12)learsspecie−s in thse(cid:12)(cid:12)detector with mteactsasebsleinevtehnetrraantgeea1t0C0DGMeVS-I<∼I mimχp01li<∼es 3a00crGosesV-seactdioen-
cnlueculse/anreumtarasslinMois,yµstieχmisµthe=remducMed/(mmass+ofMth),e annud- σciχSeIpnc>∼y ifsew30×%1fo0r−4t4hcemC2D. MIfS-wIIeeaxspsuermimeetnhtewseighnaavleeffian-
iχ χ i χ i
AandZ arethe targetnucleus massnumber andatomic effective exposure of 184 kg-days. For comparison to
number, respectively. The quantities Gps and Gns rep- the data we note that a cross-section σχSIp = 10−44cm2
resent scalar four-fermion couplings of the neutralino to for mχ01 ≃ 150 GeV implies approximately 0.5 expected
point-like protons and neutrons. They can be described events in this effective exposure.
schematically as Ascalar-scalarcross-sectionthislargeisnotgenericin
supersymmetricmodels,particularlythosewithuniversal
GN = N q¯q N (SUSY parameters) , (2) gaugino masses that tend to give rise to an overwhelm-
s q=u,Xd,s,c,b,th | | i× ingly bino-like LSP [16, 17]. Values of σχSIp in the range
forwhichCDMS-IIissensitivetendtoinvolveLSPswith
where the quantity in parenthesis is calculable once the a sizable mixture of non-bino components, particularly
details of the supersymmetric model are specified. The Higgsino components [18, 19, 20, 21, 22, 23]. This is
initial nuclear matrix elements, however, are at present because the SI cross-section is dominated by t-channel
not calculable from first principles. Their values must Higgs exchange diagrams, the size of which are deter-
be inferred from pion-nucleon scattering data. Depend- mined by the Higgsino component of the LSP. An ob-
ing on the methodology employed in this analysis, dif- servablesignalatCDMS-IIthereforealsofavorsarelative
ferent values for this important set of parameters can light CP-even Higgs mass.
be extracted – particularly for the case of the πN Σ- In Table I we presentfive benchmark points which ex-
term [11, 12, 13]. The importance of the resulting hibit event rates comparable to those recently reported
uncertainty in this parameter on predictions for dark by the CDMS-II collaboration, computed by integrat-
matter interactioncross-sectionswasrecentlyconsidered ing (3) over the range (4). We arrived at these points
in[14,15,16],whereitwasshowntobepotentiallyquite byconsideringasimpleunifiedmodelwithuniversalsca-
large. We will return to this issue at the very end of lar soft mass m0 and trilinear coupling A0 at a high-
this section. For what follows we will simply use the energy scale, here taken to be the grand unified scale
default values in DarkSUSY 5.0.4 for all nuclear matrix Λuv = 2 1016 GeV. We then introduced non-universal
elements. gaugino s×oft masses M1, M2 and M3 via
The differential rate of neutralino-nucleon scattering
events (in units of events/kg/day) can be computed Mi =m1/2(1+δi) (5)
from (1) according to
where m represents the typical scale of the soft gau-
1/2
ddER = ciρχσ2χmi|Fµi(2qi)|2 Z ∞ f(~vv,t)d3v, (3) gaipnporomacahssheassabnedenwsehwowillnctoongsiivdeersuopnelrysyδm2,mδ3et6=ric0m. oTdheilss
Xi χ iχ vmin compatible with all direct and indirect constraints, but
with relatively large spin-independent cross-sections for
where we sum over all nuclear species present, with c
i
the LSP neutralino [27, 28]. This approach is similar in
being the mass fraction of species i in the detector. The
quantityf(~v,t)d3vistheneutralinovelocitydistribution spirit to the exploration conducted in [20, 21].
Thegluinomassplaysanimportantroleinthesemod-
(presumedtobe Maxwellian)withv = ~v theneutralino
velocity relative to the detector [2]. F|in|ally F (q )2 is els, albeit an indirect one. As is well known, the gluino
i i
the nuclear form factor for species i, with q |= √2M| E soft mass M3 at the high scale influences the eventual
i i
value of the µ parameter (as determined by solving the
being the momentum transfer for a nuclear recoil with
electroweaksymmetrybreakingconditionsatthelowen-
energy E. For the purpose of this analysis we will use
ergy scale) via renormalizationgroup effects on the run-
the output differential rates from DarkSUSY, calculated
ning of the Higgs scalar soft masses [29, 30, 31]. The
via (3), over a range of recoil energies relevant to the
desired experiment. For the CDMS experiment the re- consistent choice of δ3 < 0 is therefore preferred as this
tendstodecreasethevalueoftheµparameterandhence
ported energy range considered was
an increase in the Higgsino content of the eventual LSP.
10keV Erecoil 100keV. (4) The relevant information for connecting these models
≤ ≤ to the reported signal at CDMS-II is collected in Ta-
We therefore perform a numerical integration of (3) by ble II, where we give the mass of the LSP neutralino,
constructinganinterpolatingfunctionforthedifferential the spin-independent cross-section for elastic scattering
rate sampled in 1 keV intervals. onasingleproton,andthenumberofeventsexpectedat
3
TABLE I: Soft term parameters for selected points for com- TABLE III: Predictions of the benchmark models in Table I
parison to reported CDMS signal. All soft mass parameters for other dark matter search experiments and the thermal
aregiveninunitsofGeVandallpointswereselectedtohave relic density of neutralinos. All calculations were performed
µ>0. using DarkSUSY 5.0.4.
Point A B C D E Point A B C D E
m0 750 500 350 350 350 RXe (kg−1-yr−1) 1.32 3.64 3.66 4.63 5.15
m1/2 750 500 575 575 575 NXe (Xenon10) 1.14 3.16 3.17 4.01 4.47
A0 370 270 150 150 150 NXe (Xenon100) 17.4 47.9 48.1 60.9 67.7
tanβ 25 15 30 30 30 (Φint/J¯) 1015 (cm−2 s−1) 196.8 9.27 1020.4 243.8 164.1
×
δ2 0.65 0.62 -0.6 0.82 -0.47 Φγγ/ΦγZ 0.52 0.20 0.33 0.57 0.31
δ3 -0.35 -0.3 -0.3 -0.35 -0.3 Φµ (km−2 yr−1) 114.0 171.3 63.4 130.7 123.5
σv 1025 (cm2) 1.9 0.1 23.8 2.0 4.5
h iWW ×
Ωh2 therm 0.005 0.112 0.001 0.006 0.003
|
TABLE II:Properties of theLSP and resulting CDMS-II re-
coil ratefor examples in Table I. Masses and LSP properties
were computed using SuSpect 2.41, while scattering cross-
neutralino scatters [36]. Of course accumulating more
sections and the expected number of events were computed
statistics may allow for a crude measurement of the
usingdefaultvaluesinDarkSUSY 5.0.4. Thesenumberscarry
uncertaintiesassociatedwithcertainnuclearmatrixelements, recoil energy spectrum and thus shed more light on the
as mentioned in the text. Event rates on germanium nuclei nature of the scattering particle.
assume an effective exposureof 183.6 kg-days.
Implications for Other Dark Matter Search Experi-
Point A B C D E
ments.
mχ01 (GeV) 138 190 175 112 230 Aswesawintheprevioussection,avarietyofLSPcon-
B% 3.0% 70.2% 0.3% 5.4% 40.9% figurations can give rise to the signal seen at CDMS-II.
W% 0.4% 0.4% 95.8% 0.5% 53.0% Given the low statistics in the reported data it is not al-
H% 96.6% 29.4% 3.9% 94.1% 6.1% together clear whether the events seen truly indicate the
σSI 1045 (cm2) 11.9 44.4 41.3 35.3 74.8 presenceofnew physics. Additionaldata collectionis,of
χp× course,imperativetoafirmdeterminationthatwearein-
NGe (184 kg-days) 0.51 1.36 1.30 1.65 1.90
deed seeing evidence of dark matter elastic scatters with
an effective cross-sectionof the order σ 10−44cm2.
≃
One crucial cross-check will be the next round of
CDMS-II over the energy range in (4) with an effective
results reported at xenon-based detectors. The spin-
exposure of 0.3 612=183.6 kg-days. We have deliber-
× independent interaction rates of neutralinos on germa-
ately chosen examples with a variety of neutralino mass
nium and on xenon are highly correlated. Interestingly,
matrices, as evidenced by the eigenvector of the lowest
the implied rate for neutralinos scattering on xenon in-
mass state. This LSP wavefunction composition is indi-
ferred from the CDMS-II results implies something on
catedbytheentriesB%,W%andH%whichgivetheper-
theorderofonetofiveeventsinanexposureof316.4kg-
centage of bino eigenstate, wino eignesate and Higgsino
days at Xenon10. Ten events were in fact observed in
eigenstate,respectively. Thesequantitieswerecomputed
the region where the signal was expected, but this was
using SuSpect 2.41 [32] and DarkSUSY.
consistentwith their backgroundestimation[37]. Acon-
Given the low statistics in the reported CDMS
firming signal from a liquid-xenon based detector in the
data we believe that any one of these models could
near future is therefore imperative for the supersymmet-
conceivably be giving rise to the observed recoils. As
ric interpretation of the CDMS events.
mentioned above, these interaction rates are sensitive
To compute the rate of elastic scattering on xenon-
to still uncertain input numbers associated with certain
based targets we modify the procedure of the previous
nuclear matrix elements. For example, the package
section and use an integration range for (3) that better
MicrOMEGAs [34] uses a different default value for the
reflects the sensitivities of the Xenon10 apparatus:
πN Σ-term and consequently predicts an event rate on
germanium roughly twice as large as the values give 5keV Erecoil 25keV. (6)
in Table II. We have therefore chosen examples with ≤ ≤
0.5 NGe 2.0 to be conservative in our estimates. The event rates for our benchmark points in units of re-
≤ ≤
It should also be noted that recent calculations of the coils/kg/yearare given in the first entry of Table III. In
matrix element nss¯n [35] may imply a much lower the second entry we give the expected number of signal
effective value fhor| σ|SIi, implying a more challenging events in 316.4 kg-days at Xenon10. These points are
χp
environment for interpreting the CDMS-II events as clearly in a region where the liquid-xenon experiments
4
shouldbesensitivetoasignal. Inthethirdentrywegive measurement of these high-energy photons.
theexpectedeventrateattheXenon100upgradeassum- More promising signals may come from the search
ing an exposure of 80 kg 60 days = 13.15 kg-years. for neutrinos arising from the annihilation of LSP neu-
×
Assuming adequate rejection of backgroundevents all of tralinos in a location closer to the earth, such as the
thesecandidatemodelsshouldgivecleardarkmattersig- center of the sun, where issues of the galactic halo do
nals in the earliest stages of running at Xenon100. not come into play. Again we expect relatively large
Observation of a clear signal above background in liq- differences in the flux of neutrinos between wino-like
uidxenon-baseddetectorswould(a)providesomeassur- and Higgsino-like LSPs. Some fraction of the neutrinos
ance that the effect seen at CDMS-II is truly the result can eventually exit the sun and be detected in experi-
ofdarkmatterscattering,and(b)givesomefurthersup- ments such as IceCube [43] via conversion of muon neu-
porttotheconjecturethatthisinvolveselasticscattering trinos into muons. To calculate this rate we integrate
of supersymmetric neutralinos. Even within the super- the differential flux of conversionmuons from solar-born
symmetric framework, however, it is unlikely that such as well as earth-born neutrinos over the energy range
an observation alone can distinguish between the vari- 50 GeV E 300 GeV, assuming an angular resolu-
µ
≤ ≤
ous models represented by the benchmarks in Table I. tion of 3 degrees. The nominal target area for IceCube
Several indirect detection experiments, however, may be is 1 km2, but the effective area for detection of neutri-
sensitive to the differences in the LSP wavefunctionthat nos via muon conversion is smaller and can be cast as
distinguish these models. a function of the muon energy [44, 45, 46]. Previous
The Fermi-GLAST satellite is currently surveying the observations based on a limited set of 22 strings of pho-
fluxofgammarayphotonsfromthelocationofthegalac- tomultipliertubesputalimitonthesizeofthemuonflux
tic center. If some component of this flux comes from at approximately 300-400 muons/km2/year. The fluxes
the annihilation of LSP neutralinos it may be possible for these benchmark models all fallwellbelow these lim-
to observe an increase in the flux over estimated astro- its, as shown in Table III, though well within reach of
physical backgrounds. The calculation of the flux de- the next data run at IceCube. Even with an exposure
pends on the microscopic physics of the neutralino and of only 0.2 km2-years all of these models will produce at
itsinteractions,butalsoverystronglyonthemacroscopic least 10 signal events at IceCube.
physics of the halo profile assumed for the galaxy. The Finally, we mention the implications for the observed
latter is conveniently summarized by a single parame- excess in positrons in the energy range 10-100 GeV re-
ter J¯(∆Ω) where ∆Ω represents the solid angle reso- cently measured by the PAMELA experiment [47]. It is
lution of the observatory. We consider the commonly bynowwellestablishedthatstandardMSSMmodelscan
adoptedprofileofNavarro,FrankandWhite(NFW)[38] fit the signal from PAMELA only with some difficulty.
whichgivesavalueofJ¯(∆Ω)=1.2644 104andassume For models with a significant wino or Higgsino content,
an angular resolution of ∆Ω = 10−5 ×sr. The value of the observed rate implies a thermally-averagedannihila-
the estimated gamma ray flux for photons in the energy tion cross-section in to W+W− final states on the order
range 1 GeV ≤ Eγ ≤ 200 GeV is given in Table III. of hσviWW ∼ 10−24 cm3/s [48, 49]. Such rates can be
The expected flux is generally quite large, suggesting achieved for some of the models in Table III though not
that a signal should be expected above background at forall.1 Modelswhichachievethishighannihilationrate
Fermi/GLAST in the near future. But we emphasize tendtoalsobecasesinwhichneutralinosannihilatevery
that these estimates can vary over many orders of mag- effectivelyintheearlyuniverse,resultinginadiminished
nitude if different assumptions aboutthe halo profileare thermal relic density. We chose one model (Point B)
employed. which gives a thermal relic density, as computed using
In addition to the diffuse gamma rays coming from DarkSUSY, which fits the measurement as inferred from
neutralinoannihilationsonealsoexpectsmonochromatic the WMAP three-year[51] and five-yeardata [52] which
signals from loop-induced diagrams in which two neu- we take to be
tralinos annihilate into a pair of photons (γγ line) or
into a photon and a Z-boson (γZ line) [39, 40, 41]. It 0.0855 Ω h2 0.1189, (7)
χ
≤ ≤
has been noted that the ratio of the observed gamma
rayfluxesfromthesetwoprocessesiscorrelatedwiththe atthe 2σ level. For the othercases itwill clearlybe nec-
wave-functioncompositionoftheLSP[42]. Furthermore, essary to invoke non-thermal production [53, 54, 55, 56]
takingtheratioofthefluxeseliminatesmuchofthehalo- to achieve the appropriate relic density.
model dependence from the analysis of the signal. The
ratio of the fluxes Φγγ/ΦγZ is given in Table III for our Implications for Observation of SUSY at the LHC.
various benchmark points. They differ by as much as
a factor of two. Observing these ratios, however, at at-
mospheric Chernekov telescopes will require a favorable
halomodel profileandexcellentenergyresolutiononthe 1 Seealsothebenchmarkcasesgivenin[50]
5
TABLE IV: Relevant SUSY mass spectra and total produc- TABLE V: Number of signal events for standard discovery
tion cross sections at the LHC, for the benchmark models in channels at the LHC for √s = 10 TeV for the benchmark
Table I. All masses are in GeV. models of Table I.
Point A B C D E Numbersof Events
mχ01 138 190 175 112 230 Point A B C D E
mχ02 152 254 235 130 239 Multijets 16 68 72 114 57
mχ03 326 261 505 252 504 1ℓ + jets 17 78 61 70 19
OS 2ℓ + jets 0 14 2 12 1
mχ04 1008 663 513 846 515 SS 2ℓ + jets 0 1 2 4 0
m ± 146 243 175 123 234
χ1 3ℓ + jets 0 4 0 4 0
mχ±2 1008 663 514 846 515 Significance S/√B
mg˜ 1156 847 952 890 951 Point A B C D E
mt˜1 826 607 719 544 709 Multijets 2.0 8.4 8.9 14.0 7.0
mt˜2 1284 925 862 964 865 1ℓ + jets 1.1 5.2 4.1 4.7 1.7
m˜b1 1155 853 809 766 812 OS 2ℓ + jets NA 4.4 0.6 3.8 0.3
m˜b2 1271 903 874 943 871 SS 2ℓ + jets NA 1.0 2.0 4.0 NA
mτ˜1 740 520 344 338 352 3ℓ + jets NA 2.9 NA 2.9 NA
mτ˜2 1079 724 414 752 424
m 115 112 113 114 113
h
σs7uTsyeV (pb) 1.3 0.3 1.2 2.7 0.4
σs1u0sTyeV (pb) 2.3 1.2 2.5 5.1 1.3 Given the relatively low cross-sections and reduction in
σs1u4sTyeV (pb) 4.0 4.1 5.7 10.0 3.7 leptonicsignatures(aswedescribebelow)itishighlyun-
likely that these models will give significant event rates
above the Standard Model background in 500 pb−1 or
less integratedluminosity for √s=7 TeV. However,the
A common feature of the models listed in Table I is a prospects brighten considerably at higher energies, par-
general compression of the gaugino mass spectrum rela- ticularlyifoneassumesthatmeasurementsofjet p and
T
tive to unified models such as mSUGRA. This is partic- E are reasonably reliable.
T
ularly true of the mass gap ∆± ≡ mχ±1 −mχ01 which is 6 We begin with standard SUSY discovery modes [59],
crucial to many of the standard supersymmetric search slightly modified to maximize the signal significance for
strategiesattheLHC,aswellashavingalargeimpacton these models. These five signatures are collected in Ta-
the triggeringefficiencies forsupersymmetric events. We bleVfor1fb−1 ofintegratedluminosityat√s=10TeV.
givecertainkeyphysicalmassesforthemodelsofTableI InallcaseswerequiretransversesphericityS 0.2and
T
in Table IV in units of GeV. All masses are computed at least 250 GeV of E except for the trilept≥on signa-
T
from the high-scale boundary conditions after renormal- ture,whereonlyE 6 200GeVisrequired. Themultijet
T
ization group evolution using SuSpect 2.41. channel includes6a ve≥to on isolated leptons and requires
To analyze the signatures of these models at the LHC at least four jets with the transverse momenta of the
we generated events using PYTHIA followed by a de- four leading jets satisfying p (200,150,50,50) GeV,
T
≥
tector simulation using PGS4 [57]. Sparticle decays are respectively. For the leptonic signatures we include only
calculated using SUSY-HIT [33]. Data sets represent- e± andµ± finalstatesanddemandatleasttwojets with
ing 1 fb−1 were generated for center of mass energies the leading jets satisfying p (100,50) GeV, respec-
T
√s=10TeV and√s=14TeV foreachmodel. Inaddi- tively. We also display results≥in Table VI for 1 fb−1 of
tion we considered a suitably-weighted sample of 1 fb−1 integrated luminosity at √s=14 TeV.
Standard Model background events, consisting of Drell- The multijet channel is promising already at 1 fb−1
Yan, QCD dijet, tt¯, b¯b, W/Z+jets and diboson produc- at √s = 10 TeV for all models with the exception of
tion at each √s value. Events were analyzed using level point A, which has the largest gluino mass. Points
one (L1) triggers in PGS4, designed to mimic the CMS which give a mass difference ∆± > 10 GeV are capable
trigger tables [58]. Object-level post-trigger cuts were of giving hard enough leptons to∼produce a reasonable
also imposed. We require all photons, electrons, muons signalsignificanceintheone-,andeventwo-leptonchan-
andtaustohavetransversemomentumpT 10GeVand nels. The compressed spectrum tends to result in fewer
≥
η <2.4 and we require hadronic jets to satisfy η <3. leptonic events due to the inability to trigger effectively
| | | |
The last entries of Table IV gives the totalSUSY pro- onleptonswhentheirtransversemomentumdropsmuch
duction cross-section at the LHC for center of mass en- below 10 GeV. The reduction in leptonic signal is likely
ergies of 7, 10 and 14 TeV for our benchmark points. to be a generic property of supersymmetric models that
6
TABLE VI: Number of signal events for standard discovery
channels at the LHC for √s = 14 TeV for the benchmark
models of Table I. [1] H.Goldberg,Phys.Rev.Lett.50,1419(1983)[Erratum-
ibid. 103, 099905 (2009)].
Numbersof Events
[2] G. Jungman, M. Kamionkowski and K. Griest, Phys.
Point A B C D E Rept. 267, 195 (1996).
Multijets 99 321 402 436 298 [3] G.Bertone,D.HooperandJ.Silk,Phys.Rept.405,279
(2005).
1ℓ + jets 62 336 202 310 111
[4] R.J.Gaitskell,Ann.Rev.Nucl.Part.Sci.54,315(2004).
OS 2ℓ + jets 8 45 12 45 7
[5] Z. Ahmed et al. [The CDMS Collaboration], “Results
SS 2ℓ + jets 2 19 6 16 3 from the Final Exposure of the CDMS II Experiment,”
3ℓ + jets 3 8 4 6 1 arXiv:0912.3592 [astro-ph.CO].
Significance S/√B [6] M. Kadastik, K. Kannike, A. Racioppi and M. Raidal,
arXiv:0912.3797 [hep-ph].
Point A B C D E
[7] A. Bottino, F. Donato, N. Fornengo and S. Scopel,
Multijets 6.6 21.4 26.9 29.1 19.9 arXiv:0912.4025 [hep-ph].
1ℓ + jets 2.5 13.6 8.2 12.5 4.5 [8] D. Feldman, Z. Liu and P. Nath, arXiv:0912.4217 [hep-
ph].
OS 2ℓ + jets 1.3 7.4 2.0 7.4 1.2
[9] M. Ibeand T. T. Yanagida, arXiv:0912.4221 [hep-ph].
SS 2ℓ + jets 0.8 7.2 2.3 6.0 1.1
[10] P.Gondolo, J.Edsjo, P.Ullio, L.Bergstrom, M. Schelke
3ℓ + jets 1.2 3.3 1.6 2.5 0.4 and E. A.Baltz, JCAP 0407, 008 (2004).
[11] A. Bottino, F. Donato, N. Fornengo and S. Scopel, As-
tropart. Phys.13, 215 (2000).
[12] A. Bottino, F. Donato, N. Fornengo and S. Scopel, As-
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