Search for non-thermal dark matter and new scalar boson at the LHC

Transcription

1 Search for non-thermal dark matter and new scalar boson at the LHC 2015/10/21 KPS meeting/gyeongju Namgyun Jeong*, YoungDo Oh and DongHee Kim Department of physics, Kyungpook National University KPS Oct

2 Contents Introduction Non thermal dark matter model The LHC and CMS detector Overview Data reduction Limit calculation and Result Conclusion 2/19

3 Introduction Thermal Dark matter (DM) annihilation rate Ωχh cm 3 s 1, Ωχh <σv> (WMAP measurement result) DM annihilation rate <σv> = cm 3 /s CMS collaboration, PRL (2012) LHC results Gluino and Squark mass limit potentially increased Resulting in increasing Higgsino mass limit as well DM annilation rate may be bigger than expected <σv> > cm 3 /s Dan Hoopera, Chris Kelsoa, Farinaldo S.Queiroza, Astroparticle Physics, Volume 46, June 2013 Fermi-LAT experiment Measure rate even smaller than expected DM annihilation rate can be smaller than expected <σv> < cm 3 /s DM annihilation Rate is not constant. Therefore we need to consider new DM model is based on Non thermal DM scenario. 3/19

4 The Model Lagrangian Add a minimal extension to the SM Scalar color triplet(s) A fermionic DM candidate R.Allahverdi and B.Dutta, PRD 88(2013) B.Dutta,Y.Gao, and T,Kamon, PRD 89 (2014) At least two scalar bosons are needed for the successful baryogenesis Scalar boson couples to two d-quarks or u-quark and DM DM isn t protected by parity m DM m p <m e 4/19

5 DM mass definition for baryogenesis The model require m n m X If m n Ο(GeV), n DM can 3 body decay m n > m proton + m electron is allowed by the process But DM candidate should be stable m n < m proton - m electron, m n will be stable. So we set up the mass range m proton - m electron m n m proton + m electron Therefore the model assume m DM m proton = 938 MeV/c 2 5/19

6 Top quark with Dark Matter All up-type quark can be considered as final state. However we focus on top quark Top quark can be discriminated clearer than other up type monojet production. because top quark mass is well known Dark Matter escapes detector and makes huge missing energy 6/19

7 Large Hadron Collider The LHC(Large Hadron Collider) is the largest particle accelerator in the world and located in Geneva, Switzerland. There are seven experiments installed at the LHC are ALICE, ATLAS, CMS, LHCb, LHCf, TOTEM and MoEDAL. In 2015, the LHC Run2 has started with s = 13 TeV. 27 km LHC at s = 14 TeV will take 3000 fb 1 data from We considered 3000 fb 1 data at s = 14 TeV 7/19

8 Compact Muon Solenoid The CMS is one of general purpose detectors at LHC. The CMS consists of 5 subdetector systems. Tracker, ECAL(Electromagnetic Calorimeter), HCAL(Hadronic Calorimeter), Superconducting solenoid and Muon chamber. We studied monotop + DM from non thermal model using Delphes3 simulation with CMS-like detector 8/19

9 Monotop DM search results at 8TeV CMS collaboration, PRL 114, (2015) scalar vector s-channel 330 GeV 650 GeV T.Theveneaux-Pelzer on behalf of the ATLAS collaboration, arxiv: t-channel 432 GeV Resonance channel In case of coupling a re = 0.2, cross sections are excluded in the whole mass range In case of a re = 0.1, cross sections are excluded up to m vmet = 432 GeVc 2 9/19

10 Coupling dependence check for monotop pp collision at 14 TeV Leptonic channel are considered m X1 = 500, 1000, 2000, 3000, 4000, and 5000 GeV/c 2 we consider six signal samples m X2 = 8000 GeV/c 2 in order to consider only one resonance m ndm = 938 MeV/c 2 We assume couplings λ 1 = λ 2 = λ λ = 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, Kinematics doesn t depend on coupling value. M T = transverse mass of top and DM system We consider λ = 0.1 for detector simulation. 10/19

11 Simulated MC data samples Signal m X1 = 500, 1000, 2000, 3000, 4000, 5000 GeV/c 2 Background tt, single top, W+jet, Z+jet, WW, ZZ, WZ pp collision at 14 TeV Event generation : MadGragh5 Hadronization : PYTHIA8 Detector simulation : CMS-like condition using Delphes3 11/19

12 Event selection Jet candidates were required to P T > 20 GeV/c Using jet algorithm : Anti-kt jet algorithm Parameter R (cone size)= 0.5 m X1 = 500~5000 GeV/c 2 Number of b jet = 1 requied Electron candidates were required to P T > 10 GeV/c Using ΔR = 0.4 electron isolation = I rel = p T photon + p T charged_hadron + p T neutral_hadron p T electron I rel < 0.15 Top P T 250~2500 GeV/c b-quark P T 125~1250 GeV/c Leading Jet P T >125 GeV/c MET > 100 GeV Effective mass>1000 GeV/c 2 12/19

13 P T distribution Leading Jet Generator level Reconstruction and Selection cut applied After Selection Electron Generator level Reconstruction and Selection cut applied After Selection 13/19

14 MET and Effective mass distribution Missing transverse energy(met) is defined by MET= p T Signal MET comes from DM and neutrino. Signal high energy region Background low energy region Effective mass is defined by summation of scalar sum of momenta and MET. m eff = H T + MET = p T objects + MET The m eff is used to discriminate signal from background. Effective mass > 1000 GeV/c 2 cut The m eff cut is not optimized. 14/19

15 Expected number of events (background) s = 14 TeV, L = 100 fb 1 Cut ttbar singletop Wjet zjet ww zz wz sum No cut 5.541e+07 ± e+05 ± e+09 ± e+09 ± e+06 ± e+06 ± e+06 ± e B-tagging=1 &electron isolation 2.451e+07 ± e+05 ± e+08 ± e+08 ± e+05 ± e+05 ± e+05 ± e Leading Jet P T >125 GeV/c 1.235e+07 ± ± e+07 ± e+06 ± ± ± ± e MET > 100 GeV 2.604e+06 ± ± e+05 ± e+05 ± ± ± ± e m eff > ± ± ± ± ± ±143 15/19

16 Expected number of events (signal) s = 14 TeV Cut m X1 =500GeV/c 2 m X1 =1000GeV/c 2 m X1 =2000GeV/c 2 m X1 =3000GeV/c 2 m X1 =4000GeV/c 2 m X1 =5000GeV/c 2 No cut B-tagging=1 &electron isolation Leading Jet P T >125 GeV/c MET > 100 GeV m eff > Efficiency [%] /19

17 Cross section Limit calculation and Result s= 14 TeV s= 14 TeV Excluded λ = 5, 1200 GeV/c 2 λ = 5, 2600 GeV/c 2 If no excess observed with 3000 fb 1 data, in case of λ = 5, X 1 lower than 1.2 TeV and upper than 2.6 TeV can be excluded at 95% C.L. 17/19

18 Conclusion We studied Non thermal DM scenario associated with monotop production via single electron channel in pp collision at s =14 TeV. That scenario can be expected to solve correct DM annihilation rate and baryogenesis. In this study, new boson with mass 500~5000 GeV/c 2, DM candidate mass of ~1 GeV/c 2 and coupling values are 0.001~10 are considered with Delphes fast simulation. m eff is powerful cut variable to discriminate signal from background. If no excess observed with 3000 fb 1 data, in case of λ = 5, the new scalar boson mass lower than 1.2 TeV/c 2 and upper than 2.6 TeV can be excluded at 95% CL. This model can be tested at the LHC before LS2 period as Run2. 18/19

19 Thank you 19/19

20 Back up 20/19

21 Fermionic DM candidate Scalar mediator 21/19

22 M T distribution Transverse mass is defined by M T = (ΣE T ) 2 (Σp T ) 2 Signals are shifted for the invariance mass of new scalar boson. M X1 < 1000 GeV signals have specific peak at 250 and 300 GeV/c 2 22/19

23 H T distribution Scalar sum of momenta is defined by H T = objects p T H T also has the tendency like M T and has peak at 180 and 300 GeV/c only. The backgrounds have 200 GeV/c region. H T = p T objects 23/19

24 Non thermal DM model can be compared with thermal resonant channel 24/19

25 The Model Lagrangian Incoming interaction (Interaction between new scalar boson and SM quarks) Outgoing interaction (Interaction between new scalar boson and DM + SM quark) X α (α = 1, 2) : Two charged scalars boson as mediator m Xα = O (TeV) : The mediator mass arise baryon number violating in the model n DM : Singlet fermion, DM candidate m ndm = m proton : This mass range arise baryogenesis. 25/19

26 Effective mass distribution Effective mass is defined by summation of scalar sum of momenta and MET m eff = H T + MET = p T objects + MET The m eff is used to discriminate signal from background 26/19

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