Search for Dark Ma-er and Large Extra Dimensions in the jets+met Final State in Proton-Proton Collisions at s = 13 TeV

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1 Search for Dark Ma-er and Large Extra Dimensions in the jets+met Final State in Proton-Proton Collisions at s = 13 TeV Emine Gurpinar (Texas Tech University) on behalf of the CMS Collaboration PPC2017, May 22-26, 2017

2 Introduction Existence of dark ma-er: strong evidence for Beyond the Standart Model Known to us for over 80 years 26% of the total energy of the universe weakly interacting massive particle(wimp), dark (no color and no electric charge), long-lived, non baryonic, not hot Evidence through gravitational effects from rotation curves gravitational lensing Three main searches: Ø direct detection- DM-nucleon scauering Ø indirect detection-dm annihilation Ø production at colliders-production of DM in high energy particle collision LHC plays a unique role in the search for dark mauer. allows for unprecedented understanding in the behaviour of dark mauer. E. Gurpinar - PPC2017 2

3 Framework for Monojet Simplified models are used, involving a single mediator (Z ) and a single type of WIMP (χ). Mediator: scalar/pseudo-scalar or vector/axial-vector, coupling to both SM and DM sectors Parameters: mediator mass and width (m Z, Γ Z ) ; DM mass (m χ ) ; mediator couplings ( g q ; g χ ) Simplified model (Run 2) EFT model (Run 1) 3

4 Dark Ma-er Production : Monojet Search for dark mauer particles produced in association with high p T jets. q Z 0 Dark mauer particles: produced in pairs, escape the detector undetected. q q g The dark mauer system needs to recoil against some detectable object in the event to produce large MET in the event. Total momentum in the event has to be balanced. Look for initial state radiation events, q radiates energetic jet. 4

5 Mono-jet Event Selection Data (35.9 f -1 ) : MET dataset from CMS experiment (2016) The signal event contains a high p T jet and large MET. Base Line Event Selection: MET > 250 GEV Leading Jet (AK4) p T > 100 GeV with η <2.5 min φ (MET, jets) > 0.5 No loosely identified leptons (e,µ) suppress DY+jets and W+jets No loosely identified photons suppress γ+jets No identified b-jets suppress top-backgrounds Lepton, photon and b-jets veto is relaxed. For control region For signal region 5

6 Monojet Experimental Signature Large MET from the invisible mediator decaying into dark mauer particles. No leptons (muons, electrons, taus), no photons The existence of Missing Transverse Energy in the event might be Dark Ma-er 6

7 Main Backgrounds Main Backgrounds: Z νν is the main background and is irreducible W lν when lepton is out of acceptance or not identified Minor Backgrounds: Di-boson: WZ/ZZ mainly, relevant in mono-v Top: mainly from semi-leptonic Ubar DY+jets γ+jets QCD multijets when jets are highly mis-measured 7

8 Background Estimation CR: Gamma Jets CR: W (ev) jets Fit performed simultaneously in different regions. SR: Z(νν) jets CR: Z (mm) Jets CR: Z (ee) Jets 5 Control Regions (CR) (Zee, Wev, Zmm, Wmv, GJets) to estimate major bacground in the Signal Region(SR). SR: W(lν) jets CR: W (mν) Jets 8

9 Signal Region Result PAS-EXO Comparison between data and the post-fit background prediction in the signal region in the mono-jet. Events are primarily selected with MET cuts in exponentially dumping MET spectra. Major remaining background are events with Z(νν) or W(lν) with lost lepton. 9

10 Dark Ma-er Interpretation Data is found to be compatible with SM prediction. The results are interpreted in terms of simplified models containing of a pair of DM particles, that couple to a vector, axial-vector, scalar, or pseudoscalar mediator. PAS-EXO PAS-EXO Exclusion limits at 95% CL on the µ = σ/σth in the mmed mdm plane assuming vector (left) and axial-vector (right) mediators. 10

11 Dark Ma-er Interpretation PAS-EXO PAS-EXO % CL upper limits on the signal strength µ = σ/σ th as a function of the mediator mass for the scalar mediators (left). Exclusion limits at 95% CL on the µ = σ/σ th in the m med m DM plane assuming pseudoscalar (right) mediators. 11

12 Comparision with Direct/Indirect Detection PAS-EXO PAS-EXO PAS-EXO Exclusion limits at 90% CL in the m DM versus σ SI/SD plane for vector (left) axialvector (middle) mediator models. Limits (right) for the pseudoscalar mediator are compared to the the velocity averaged DM annihilation cross section upper limits from Fermi-LAT. 12

13 ADD Large Extra Dimension Model ADD model is a model framework. auempts to solve the hierarchy problem by explaining the weakness of gravity relative to the other forces, proposed by Arkani-Hamed,Dimopoulos and Dvali (ADD). The SM particles and gauge interactions are confined to the ordinary space-time dimensions, whereas gravity is free to propagate through the entire multidimensional space. Graviton predicted in ADD model can be produced at the LHC, with n extra dimensions and reduced Planck Scale M D (TeV-scale gravity). Graviton escapes detection and gives large missing energy. Final State : gluon/quark + MET Gluon to balance momentum in transverse plane. g g g G q q g G g g q G arxiv:hep-ph/

14 ADD-Results PAS-EXO PAS-EXO The 95% CL lower limits on the M D in the ADD model as a function of extra spatial dimensions n. The exclusion is found to be varying between 10 TeV for n = 2 to 5 TeV for n = 6. Upper limit and the theoretically calculated ADD graviton production crossection for n = 2 extra dimensions as a function of M D is also shown. 14

15 Fermion-Portal Model Fermion-Portal Model: one of the simplified dark mauer models. t-channel production where DM is coupled to a scalar mediator and SM fermions g u g The exclusion up to 1.4 TeV on m φ and DM masses up to 600 GeV are excluded. u u ū u u u The dark mauer candidate is assumed only to couple to up-type quarks with a coupling constant λu, which is universal in flavor i.e. identical for (u,c,t). Model parameters: (m φ, m X ) φ only coupled to up-type quarks arxiv: PAS-EXO % CL expected (black solid line) and observed (red solid line) limit for Dirac dark mauer with the coupling to the up quark corresponding to λ u = 1 in the m φ m χ plane. The blue line represent the upper bound from the relic density. 15

16 Summary CMS has performed search for dark mauer in association with jets. No excess over SM is observed in full 2016 data. Results were translated to exclusion limits. Most of them were interred with the Simplified Model. The upper limits are also computed on M D in the context of ADD ED model. Lastly the limits are also presented for Fermion Portal DM model in the plane of m φ m χ for the coupling of λ u = 1. 16

17 Back-up 17

18 Electroweak Bacground Estimation Transfer factor R to go from the the dimuon control region to the Z νν background in the signal region N i is the number of events in bin i of the recoil distribution, R i is the transfer factor between the dimuon control region and Z νν background. Other transfer factors are constructed in an analogous manner. In all we consider 5 transfer factors: 1. dimuon CR to Z νν background 2. dielectron CR to Z νν background 3. γ+jets CR to Z νν background 4. single muon CR to W+jets background 5. single electron CR to W+jets background We also use a constraint that connects the Z νν background in the signal region to the W+jets background in the signal region. 18

19 Maximum Likelihood Fit Combined Maximum likelihood fit is performed using a likelihood that is constructed as follows: 19

20 Control Regions PAS-EXO PAS-EXO PAS-EXO γ + jets control region dilepton control region single-lepton control region 20