Dark Matter Models and LHC Implications Tim M.P. Tait

Transcription

1 Dark Matter Models and LHC Implications Tim M.P. Tait University of California, Irvine Detecting Dark Matter with Gamma Rays SLAC, October 13, 2011

2 Outline Introduction: Defining the particle physics of dark matter. Some popular models Dark matter interactions Portals to communicate with the Standard Model LHC Searches Searches for supersymmetry Generic searches for missing energy Outlook

3 A Particle View of Dark Matter As a particle physicist, my job is to explore how dark matter fits into the bigger picture of particles. What do we know about dark matter? Dark (neutral) Cold (massive) Stable (or with a lifetime of the order of the age of the Universe itself). Cold Dark Matter: An Exploded View by Cornelia Parker Nothing in the Standard Model of particle physics fits the description.

4 Particle Description In general, we often find candidates for dark matter in theories for physics beyond the Standard Model. Let s take a step back from specific visions and consider how to construct a minimal sketch: Spin (behavior under Lorentz transformations) Scalar, fermion, vector,... ; Dirac/complex or Majorana/real? SM Gauge representation Charged under the SM SU(2) x U(1) or not? (Other) interactions with the Standard Model Mechanism stabilizing the DM against decay. $59.99 for 20 servings Available in Blue Raspberry, Fruit Punch, and Grape flavors...

5 (Quasi) Stable One of the mysteries of dark matter is why it is massive but (to good approximation) stable. We need a symmetry (at least approximately) to prevent dark matter particles from decaying. The simplest example is a new kind of parity forbidding a single WIMP coupling to the SM. The stabilization symmetry is one of the primary discriminants between models. This symmetry will often suggest the form of dark matter interactions with the SM. It will also sometimes determine important WIMP properties such as spin and electroweak interactions. χ decays. The number of χ s is conserved.

6 Models (a few)

7 Supersymmetry: Supersymmetry (SUSY) a ne The most famous candidate for dark matter is a supersymmetricbeyond particle. the Higgs Boson Every SM particle gets a superpartner whose spin differs by 1/2. Beyond thesymmetry Higgs Boson of upersymmetry: a new Phenomenologically viable models of supersymmetry usually include an R-parity, Supersymmetry: a isnew symmetry o which insures the lightest super-particle stable, and could be dark matter. SUSY particle production at the LHC Avoids potential problems like p decay. SUSY has a catalogue of other features: Solution to the hierarchy problem Gauge coupling unification

8 SUSY Interactions γ e e If we break supersymmetry softly, the masses of the superpartners will separate, but the interactions remain fixed by supersymmetry. ~ γ e α EM Despite having many, many new parameters, SUSY theories inherit a huge structure from the SM. e~ This implies that many things can be calculated in supersymmetric theories in terms of the masses of the superpartners. γ e~ e~ γ γ e~ e~

9 Universal Extra Dimensions Another theory of dark matter has Universal Extra Dimensions. In addition to the large dimensions we are familiar with, there is one or more small, curled up dimensions. R smaller than a few hundred GeV -1. All of the quantum fields are functions of the four large (ordinary) coordinates as well as the extra (compact) coordinates. UED does not naturally solve the hierarchy problem, but can motivate the number of fermion generations from anomaly cancellation. 4 large dimensions 5th dimension

10 Kaluza-Klein Particles The translational invariance along the extra dimensional direction implies conservation of p5, or in other words, of KK mode number. Clearly, all fields must live universally in the extra dimension for there to be translational invariance. The conserved KK number implies that the Lightest Kaluza-Klein Particle is stable. Usually the n=1 KK Photon. Every SM particle has a tower of KK modes. From the extra dimensional point of view: a photon is massless and cannot be dark matter, but if one is circulating around in a hidden dimension, to an outside observer it appears to be a massive particle at rest.

11 T-Parity Another symmetry which can stabilize dark matter is T-parity. T-parity is a phenomenological symmetry which can be invoked (usually in Little Higgs models) to protect precision measurements from large contributions from new physics. g2 M 2 Forbidden If one requires the new particles to couple in pairs, they can t contribute to SM processes at tree level, and first appear at loop level. This implies the lightest new particle is stable. R-parity and KK-parity are both examples. We can still address the hierarchy problem, which is a problem with loop diagrams. g2 g 2 16π 2 M 2 Allowed (but a lot smaller)

12 Dark Matter Interactions

13 Dark Matter Interactions χ WIMPs χ SM Particles χ SM Particles WIMPs χ Indirect Detection χ WIMPs Collider Searches χ SM Particles Direct Detection Dark matter interactions with SM particles allow indirect searches for annihilation products, direct scattering searches, and production at colliders.

14 Relic Density If dark matter is a thermal relic, annihilation into the SM also control its abundance in the Universe. In equilibrium with the SM plasma. As the temperature falls, the number of WIMPs does too. We track the equilibrium density until freeze-out: n eq σv H (mt ) 3/2 e m/t g 4 m T log MPl m m 2 T 2 M Pl m 0 GeV : m T 40 Feng, ARAA (20)...leading to the final relic abundance.

15 Relic Density If dark matter is a thermal relic, annihilation into the SM also control its abundance in the Universe. In equilibrium with the SM plasma. As the temperature falls, the number of WIMPs does too. We track the equilibrium density until freeze-out: n eq σv H (mt ) 3/2 e m/t g 4 m T log MPl m m 2 T 2 M Pl m 0 GeV : m T 40 Feng, ARAA (20)...leading to the final relic abundance.

16 Relic Density If dark matter is a thermal relic, annihilation into the SM also control its abundance in the Universe. In equilibrium with the SM plasma. As the temperature falls, the number of WIMPs does too. We track the equilibrium density until freeze-out: n eq σv H (mt ) 3/2 e m/t g 4 m T log MPl m m 2 T 2 M Pl m 0 GeV : m T 40 Feng, ARAA (20)...leading to the final relic abundance.

17 Relic Density If dark matter is a thermal relic, annihilation into the SM also control its abundance in the Universe. In equilibrium with the SM plasma. As the temperature falls, the number of WIMPs does too. We track the equilibrium density until freeze-out: n eq σv H (mt ) 3/2 e m/t g 4 m T log MPl m m 2 T 2 M Pl m 0 GeV : m T 40 Feng, ARAA (20)...leading to the final relic abundance.

18 Dark Portals We can classify dark matter s interactions based on how they make contact with the SM fields. These are also relevant for how the LHC could hope to produce dark matter. Lorentz invariance and gauge invariance (and the fact that dark matter must be electrically neutral) put strong constraints on the possible interactions. I ll classify potential interactions as: The Z portal The Higgs portal Heavy particles / contact interactions Exotic light mediators

19 The Z Portal A WIMP charged under the electroweak interaction can have couplings to the Z boson. Light dark matter (< 45 GeV) is constrained by the LEP/SLC measurements of the Z decay width. Direct detection experiments highly constrain a Dirac or complex WIMP. Electroweak WIMPs necessarily have charged sibling particles, with masses split by electroweak breaking. LEP bounds on new charged particles: mχ+ > 0 GeV or so. Measurement Fit O meas O fit /σ meas Δα (5) had (m Z ) ± m Z [GeV] ± Γ Z [GeV] ± σ 0 had [nb] ± R l ± A 0,l fb ± A l (P τ ) ± R b ± R c ± A 0,b fb ± A 0,c fb ± A b ± A c ± A l (SLD) ± sin 2 θ lept eff (Q fb ) ± m W [GeV] ± Γ W [GeV] ± m t [GeV] ± July

20 The Higgs Portal July 2011 Theory uncertainty Δα (5) had = ± ±0.000 incl. low Q 2 data m Limit = 161 GeV Δχ 2 3 A scalar WIMP can have renormalizable interactions with the SM Higgs boson, which could conceivably dominate if most of the new physics is heavy: L = 1 2 λχ2 H 2 This interaction does not necessarily imply the WIMP itself is electroweakly charged. In many (particularly SUSY) models, the Higgs portal is one of the key interactions dominating direct detection signals. #!$!"#$ #$ #!!$ 2 1 Excluded LEP EW m H [GeV] Working Group %&'()*+,$-./##0$&12&3)&4$ %&'()*+,$-./##0$+56&*'&4$ V Sharma, Lepton-Photon 2011

21 Heavy Particles... q Interactions between dark matter and the SM could go through heavier particles (than the WIMP itself). The most popular models of dark matter work this way: SUSY, UED, Little Higgs,... In these models, these heavy states are themselves charged under the SM gauge interactions. Which interactions will ultimately be most important depends on which of these new particles have the strongest interactions with dark matter and lightest masses. q~ e ~ χ ~ q e G. Bertone

22 ...Contact Interactions In the limit where the heavy particle masses become heavier than the momentum transferred in the process of interest, they simplify into contact interactions. In this limit, one can capture a variety of models by focusing on the contact interactions in an Effective Field Theory, forgetting the underlying UV theory. Some types of interactions, such as through a WIMP magnetic moment, are necessarily contact interactions. χ χ χ g 2 M 2 q q q q G eff q 1 M χ σ µν χ F µν E.g. Magnetic inelastic DM: Chang, Weiner, Yavin [ ] Lin, Finkbeiner [ ] χ q

23 Light Mediators ! " S Dark matter could have its own dark force, mediated by a light(ish) force carrier that is only weakly coupled the the Standard Model. The PAMELA (and now Fermi) positron excess motivates such a force, because of the tension between the rate of annihilation required to produce a large enough signal compared with the relic density. A popular idea to reconcile the two is to introduce a light mediator (such as a dark photon) to invoke a Sommerfeld-like enhancement at small WIMP velocities ! v φ m αm Cirelli, Kadastik, Raidal, Strumia Arkani-Hamed, Finkbeiner, Slatyer, Weiner γ d... v v α 0 2 1

24 The LHC and Dark Matter

25 An LHC s Eye View of WIMPs Dark matter is expected to be too weakly interacting to be reliably detected in the LHC detectors. Seeing their production is thus all about discovering something missing in LHC events. If there are colored heavy particles to produce, we can make them and watch them decay into WIMPs. Otherwise, we will have to look for WIMPs produced along with hadronic radiation. The Standard Model already produces neutrinos which escape from LHC detectors. χ χ KK Sgluquarkino Pair Production Followed by Decay into WIMPs Maverick Production χ χ

26 LHC SUSY Searches q Searches for SUSY at the LHC typically fall into the former category: at a microscopic level, the LHC collides quarks and gluons, and will most easily produce colored super-partners. The squarks or gluinos can have complicated cascade decays down into dark matter, producing extra hard jets and sometimes leptons. Energy distributions of the decay products reflect the masses of the parent particles and intermediate steps in the cascade. ~g q~ Ehrenfeld, SUSY 2011 q χ ~ W + e + ν ~ χ "#$%&'# ()*(#+,''#

27 CMSSM Limits Including Before EPS 68% CL 95% CL CMSSM P( 2 ) > 5% A lot of searches are done in the framework of msugra (closely related to cmssm), which assumes a set of 4+1 parameters determine the super-particle spectrum: M0: Universal scalar mass M1/2: Universal gaugino mass A0: Universal A-term Tan β: Ratio of Higgs VEVs De Roeck, DMUH11 2 probability: P( 2 ) for CMSSM Before EPS: 16% Including CMS@EPS: 11% CMS searches significantly constrain allowed SUSY parameter space. The air is getting very thin for constrained SUSY models but it needs more data to be fully conclusive. More in the backup (incl. ATLAS) We will know more after summer, but have to start preparing Sgn(μ): Phase of the supersymmetric Higgs mass parameter. Melzer-Pellmann, SUSY 2011

28 Squarks and Gluinos More generally, one can use searches for missing energy plus various numbers of jets to put bounds on squark and/or gluino production. Gluinos decay to two jets + WIMP Squarks into one jet + WIMP =<ST For equal masses, searches require them to be larger than about 1 TeV Limits are still several hundred GeV when one or the other is very heavy. Limits can be evaded if the decay leads to very soft decay products (such as from a degenerate spectrum/cascade).!""#$%&'() *'+', -./ +'0**'1%2 ' =<ST Ehrenfeld, SUSY 2011

29 Is SUSY in Trouble? Some people have interpreted these null searches as SUSY being in trouble or disfavored. My opinion is that this conclusion is premature (even for msugra). SUSY s primary motivation is to solve the hierarchy problem. From this point of view, the most crucial sparticle is the scalar top, and limits still leave open natural regions of parameter space. Ehrenfeld, SUSY 2011 O*&8:A&8:<:79)'<!P##P=! QRS7, 5,,> T 5U!V!511W! This search is relevant for gluinos heavier than stops; the other case, including direct searches for stops needs more data and are ongoing.

30 Simplified Models One can step away from specific MSSM assumptions by working with simplified models. These are phenomenological sketches of theories with some basic particles and decays built into them. For a catalog: Alves et al The experimental collaborations decay have been willing to explore 600 casting their SUSY searches into this 400 framework, allowing for a much more flexible interpretation of limits. m Χ GeV body direct cut NAME ch MET (Ge De Roeck, DMUH11 1 Dijet High MET 2 + j > Trijet High MET 3 + j > Multijet Low MET 4 + j > 0 5 Multijet High HT 4 + j > Multijet Moderate MET 4 + j > Multijet High MET 4 + j > 350 m Χ GeV body direct decay 0 Alves, Izaguirre, Wacker [ ] m g GeV m g GeV

31 What does this mean for Dark Matter? Is there a take home message for DM? Neutrinos from Ice Cube Cotta, Howe, Hewett, Rizzo arxiv: In msugra, gaugino masses are tightly correlated: MLSP ~ Mgluino / 7. In more general SUSY models, the colored particles are usually among the least relevant ones for dark matter phenomenology. pmssm E.g. IceCube vs LHC.

32 Cosmic Neutralino Signals A handle on the electroweak particles from LHC could tell us lots about DM. These properties can be directly relevant for annihilation in the halo. SUSY has Majorana particles which tend to annihilate into heavier fermions and/or W bosons. Fermi searches for bb spectra... Loops of charged particles allow them to annihilate into γγ or γz. A smoking gun signal... d(σv)γ/deγ [ 29 cm 3 s 1 TeV 1 ] TeV (Mostly) Higgsino LSP Bergstrom, Bringmann, Eriksson, Gustafsson hep-ph/ E γ [TeV]

33 Cosmic Neutralino Signals A handle on the electroweak particles from LHC could tell us lots about DM. These properties can be directly relevant for annihilation in the halo. SUSY has Majorana particles which tend to annihilate into heavier fermions and/or W bosons. Fermi searches for bb spectra... Loops of charged particles allow them to annihilate into γγ or γz. A smoking gun signal! ~ χ + W W d(σv)γ/deγ [ 29 cm 3 s 1 TeV 1 ] W W W 1.5 TeV (Mostly) Higgsino LSP Bergstrom, Bringmann, Eriksson, Gustafsson hep-ph/ E γ [TeV] γ γ

34 Monojets The second class of searches looks for monojets -- ordinary jets of hadrons recoiling against WIMPs. These searches put bounds on the coefficients of higher dimensional operators whereby WIMPs interact with quarks or gluons in the EFT. Experimental searches already exist, designed to look for KK gravitons in theories with large extra dimensions. Beltran, Hooper, Kolb, Krusberg, TMPT, JHEP 09:037 (20) Probability distribution / GeV p (GeV) T,jet Tevatron mχ = 5 GeV Rajaraman, Shepherd, TMPT, Wijanco [ ] See also: Fox, Harnik, Kopp, Tsai [ ]

35 Colliders - Direct Detection CoGeNT limits Tevatron quarks CoGeNT favored 2 Tevatron G CRESST limits exclusion LHC qq 5 reach Goodman, Ibe, Rajaraman, Shepherd, TMPT, Yu ) 2 (cm -41 N SI CDMS limits Xenon limits -44 SCDMS reach Xenon 0 reach LHC G 5 reach m (GeV) 2 3 Similar Results: Bai, Fox, Harnik

36 Spin-Dependent -36 PICASSO p limits Goodman, Ibe, Rajaraman, Shepherd, TMPT, Yu KIMS p limits Xenon n limits DMTPC p reach ) 2 (cm! N SD µ "# # 5 "q# # 5 q Tevatron exclusion µ Tevatron limits were already excluding the parameter space of current and near-future direct searches for spin-dependent scattering of WIMPs with masses < about 300 GeV! -42 µ "# # 5 "q# # 5 q LHC 5! reach µ m " (GeV) 2 3 Similar Results: Bai, Fox, Harnik

37 Gamma-Ray Lines χ q s -1 ) 3 (cm Majorana WIMP SD-interaction Direct Detection Tevatron m (GeV) (old) Fermi limits (NFW profile) Goodman, Ibe, Shepherd, Rajaraman, TMPT, Yu χ The effective theory language can also be effectively mapped into indirect searches for dark matter. For example, interactions with quarks can be closed into loops and turned into annihilation into gamma ray lines. The Fermi limits are actually the best ones for some operators (such as for spin-dependent interactions). One could also study continuum annihilation signals in the EFT framework.

38 Gamma ray Lines and MiDM Gamma ray line bounds also have something interesting to say about the Magnetic inelastic DM models. In this case, WIMPs can annihilate into a two photons at tree level through their magnetic moment interactions. The Fermi line constraints are particularly relevant for lower mass WIMPs. s -1 ) 3 (cm "!! (old) Fermi limits Goodman, Ibe, Shepherd, Rajaraman, TMPT, Yu Magnetic inelastic DM Chang et al [ ] MiDM 90% MiDM 99% -30 m # (GeV) 2

39 How Effective a Theory? How good is the EFT approximation? It depends on the momentum transfer of the process.? Direct Detection: Q 2 ~ (50 MeV) 2. EFT should work well unless you have ultralight mediators. Annihilation: Q 2 ~ M 2. Fine in SUSY-like theories, problematic for quirky WIMPs or maybe coannihilators. Colliders: Q 2 ~ pt 2 Bounds are generically too conservative for colored mediators. ΣSD p cm dγ 5 d ΧΓ 5 Χ uγ 5 u ΧΓ 5 Χ sγ 5 s ΧΓ 5 Χ MDDM GeV --> 1 GeV KIMS PICASSO MDDM Too stringent for light neutral mediators Bai, Fox, Harnik m Χ GeV

40 How Effective a Theory? How good is the EFT approximation? It depends on the momentum transfer of the process.? Direct Detection: Q 2 ~ (50 MeV) 2. EFT should work well unless you have ultralight mediators. Annihilation: Q 2 ~ M 2. Fine in SUSY-like theories, problematic for quirky WIMPs or maybe coannihilators. Colliders: Q 2 ~ pt 2 Bounds are generically too conservative for colored mediators. ΣSD p cm dγ 5 d ΧΓ 5 Χ uγ 5 u ΧΓ 5 Χ sγ 5 s ΧΓ 5 Χ MDDM GeV --> 1 GeV KIMS PICASSO MDDM Too stringent for light neutral mediators Bai, Fox, Harnik m Χ GeV

41 Outlook A particle description of dark matter involves specifying the WIMP spin, EW representation, and portal of interaction with the SM. These specific choices have tangible effects on the signals we expect at the LHC, in direct detection, and indirect detection. (More from Doug next...) The LHC can make relevant statements about dark matter, but they depend strongly on the theory. SUSY theories are becoming well-constrained with respect to their colored sparticles, but the most relevant sparticles for dark matter are still rather unconstrained. This situation will change with time; the LHC is really just beginning... Monojets provide an interesting and orthogonal probe of DM models. Ultimately, interplay between experiments can help make a discovery!

42 Bonus Material

43 R-Parity By itself, supersymmetry does not imply a stable massive particle. It has interactions which would naively violate baryon and lepton number, and do scary things like make protons decay. The usual take on this is to simply forbid all of these interactions by invoking a symmetry: R-parity. R-parity insures that the superpartners only couple in pairs to the SM. It produces a stable particle! u { p d u s R P ( 1) 3(B L)+2S SM particles: +1 Superpartners: -1 e + ū u { π 0

44 Motivations for SUSY X SUSY has a lot of good motivation independently from its being a theory of dark matter. H H The original motivation was to address the gauge hierarchy problem: the fact that the Higgs VEV is very sensitive to quantum corrections. If there is some heavy particle which couples to the Higgs (i.e. a GUT gauge boson), quantum corrections try to drive the Higgs mass to its own mass. SUSY cancels these large corrections by adding additional diagrams containing the superpartners. H g2 GUT 16π 2 M 2 X X ~ H ~ g2 GUT 16π 2 M 2 e X M 2 X M 2 e X v 2 : No fine-tuning! H

45 In fact, there are some generic trends that come about from the renormalization group. Identity of the LSP If the Lightest Supersymmetric Particle is stable, any superpartners present in the early universe will eventually decay into them. msugra The LSP had better turn out to be neutral if we would like it to play the role of dark matter. For a given model of SUSY breaking, we can calculate the spectrum and determine which particle is the lightest. K. Olive, astro-ph/

46 Neutralino Dark Matter In the MSSM, the 4 neutralinos are Majorana fermions which are mixtures of the superpartners of W3, B, and the two neutral Higgses. χ 0 1 = N 11 B + N12 W3 + N 13 H N 14 H 0 2 As a result, their interactions are a little complicated: it depends on what admixture of each state is present. The RGEs typically result in an LSP which is mostly Bino, with a small amount of Higgsino and W3ino. Specific models of SUSY breaking may upset these expectations. AMSB: W3ino WIMP Bino: Couples to g1 Y (interactions with the SM involve the sfermions) B f f

47 Neutralino Dark Matter In the MSSM, the 4 neutralinos are Majorana fermions which are mixtures of the superpartners of W3, B, and the two neutral Higgses. χ 0 1 = N 11 B + N12 W3 + N 13 H N 14 H 0 2 As a result, their interactions are a little complicated: it depends on what admixture of each state is present. The RGEs typically result in an LSP which is mostly Bino, with a small amount of Higgsino and W3ino. Specific models of SUSY breaking may upset these expectations. AMSB: W3ino WIMP W3ino: Couples to g2 T3 (interactions with sfermions and W -- not Z! -- bosons) W W 3 W +

48 Neutralino Dark Matter In the MSSM, the 4 neutralinos are Majorana fermions which are mixtures of the superpartners of W3, B, and the two neutral Higgses. χ 0 1 = N 11 B + N12 W3 + N 13 H N 14 H 0 2 As a result, their interactions are a little complicated: it depends on what admixture of each state is present. The RGEs typically result in an LSP which is mostly Bino, with a small amount of Higgsino and W3ino. Specific models of SUSY breaking may upset these expectations. AMSB: W3ino WIMP Higgsino: Couples to massive particles H 0 t Z t H 0 H 0

49 Neutralino Dark Matter In the MSSM, the 4 neutralinos are Majorana fermions which are mixtures of the superpartners of W3, B, and the two neutral Higgses. χ 0 1 = N 11 B + N12 W3 + N 13 H N 14 H 0 2 As a result, their interactions are a little complicated: it depends on what admixture of each state is present. The RGEs typically result in an LSP which is mostly Bino, with a small amount of Higgsino and W3ino. Specific models of SUSY breaking may upset these expectations. AMSB: W3ino WIMP Higgs interactions are hybrids... H 0 H 0 W or B

50 Annihilation Now we have everything we need to look at neutralino annihilations. This is a complicated process... but we can understand some general features. Neutralinos are Majorana fermions. In the non-relativistic limit, they are Pauli-blocked from an initial S=1 state. No annihilation through an s-channel vector particle. Sfermion exchange likes to produce SM fermions of like-chirality, (S=1) and is suppressed by mf for an S=0 initial state. ~ Higgsino x Gaugino m2 f m 2 χ ~ Higgsino or W3ino Bottom Line: Suppressed σv leads to generically too many Binos.

51 Gauge Coupling Unification A by-product of the Minimal Supersymmetric Standard Model is improved gauge coupling unification. SM In the SM, the gauge couplings approach each other, but don t actually converge. Somewhat miraculously, adding the MSSM particle content at the ~ TeV scale deflects the running and produces a convergence of the couplings. MSSM Is this a mirage or nature telling us something?

52 Example EFT: Majorana WIMP As an example, we can write down operators of interest for a Majorana WIMP. There are leading operators consistent with Lorentz and SU(3) x U(1)EM gauge invariance coupling the WIMP to quarks and gluons. Gluon operators are normalized by αs, consistent with their having been induced by loops of some heavy colored state. Each operator has a (separate) coefficient M* which parametrizes its strength. Name Type G χ Γ χ Γ q M1 qq m q /2M M2 qq im q /2M 3 γ 5 1 M3 qq im q /2M 3 1 γ 5 M4 qq m q /2M 3 γ 5 γ 5 M5 qq 1/2M 2 γ 5 γ µ γ µ M6 qq 1/2M 2 γ 5 γ µ γ 5 γ µ M7 GG α s /8M M8 GG iα s /8M 3 γ 5 - M9 G G α s /8M M G G iα s /8M 3 γ 5 - G χ [ χγ χ χ] G 2 G χ [ qγ q q][ χγ χ χ] q Other operators may be rewritten in this form by using Fierz transformations.

53 Jets + MET CDF has a monojet search aimed at ADD large extra dimensions, where the jet is recoiling against one of a tower of KK gravitons. Event Selection: Leading jet PT > 80 GeV. Missing ET > 80 GeV. 2nd jet allowed PT < 30 GeV. Veto more jets PT > 20 GeV. Veto isolated leptons with PT > GeV. Based on 1 fb-1, CDF constrains new physics (after cuts) contributions to σ < 0.6 pb. CDF, mono_jet/public/ykk.html

54 Backgrounds To calibrate our simulations, we reproduce the CDF background using MadEvent with PYTHIA and PGS [CDF detector Model]. Including NLO k-factors, we succeeded at the % level. The dominant physics backgrounds are: Z + jets (with Z-> νν). W + jets (W->eν with the e lost). The QCD background from jet mismeasurements creating fake missing energy is subdominant, as determined by CDF itself. (And we don t try to simulate it). Beltran, Hooper, Kolb, Krusberg, TMPT, JHEP 09:037 (20) q q q q W + Z jet ν l + jet ν ν