Dark matter searches with mono-photon signature at future e+e− colliders Jan Kalinowskia, Wojciech Kotlarskib, Krzysztof Mekalaa, Pawel Sopickia, Aleksander Filip Zarnecki_ a a Faculty of Physics, University of Warsaw b Institut f¨urKern- und Teilchenphysik, TU Dresden Research supported by XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects Electroweak Physics and Beyond the Standard Model session April 14, 2021 A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 1 / 16 Outline 1 Introduction 2 Analysis framework 3 Results 4 Conclusions A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 2 / 16 Introduction Dark Matter production The mono-photon signature is considered to be the most general way to look for DM particle production in future e+e− colliders. DM can be pair produced in the e+e− collisions via exchange of a new mediator particle, which couples to both electrons (SM) and DM states This process can be detected, if additional hard photon radiation from the initial state is observed in the detector... Considered in this contribution is radiative DM production at high energy e+e− colliders: 500 GeV ILC and 3 TeV CLIC. A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 3 / 16 Introduction International Linear Collider Technical Design (TDR) completed in 2013 arXiv:1306.6328 superconducting accelerating cavities 250 { 500 GeV c.m.s. energy (baseline), 1 TeV upgrade possible footprint 31 km polarisation for both e− and e+ (80%/30%) A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 4 / 16 Introduction Compact LInear Collider Conceptual Design (CDR) presented in 2012 CERN-2012-007 high gradient, two-beam acceleration scheme staged implementation plan with energy from 380 GeV to 3 TeV footprint of 11 to 50 km e− polarisation (80%) For details refer to arXiv:1812.07987 A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 5 / 16 Introduction Running scenarios ILC Total of 4000 fb−1 assumed at 500 GeV (H-20 scenario) 2×1600 fb−1 for LR and RL beam polarisation combinations 2×400 fb−1 for RR and LL beam polarisation combinations assuming polarisation of ±80% for electrons and ±30% for positrons arXiv:1903.01629 CLIC Total of 5000 fb−1 assumed at 3 TeV 4000 fb−1 for negative electron beam polarisation 1000 fb−1 for positive electron beam polarisation assuming polarisation of ±80% for electrons arXiv:1812.06018 A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 6 / 16 Introduction Unique analysis approach 4000 Most of the studies performed so far Vector, 500GeV ILD focused on heavy mediator exchange [GeV] 95 3000 Λ expected WIMP (EFT limit) and coupling values O(1) exclusion region ) extracted were limits on DM 2000 Only statistical uncertainties _ or mediator masses 4ab-1, P(e ,e+) = (+80%,-30%) 1000 4ab-1, polarisation mix _ 1.6ab-1, P(e ,e+) = (+80%,-30%) 4ab-1, unpolarised In our study: EFT not valid 50 100 150 200 250 focus on light mediator Mχ [GeV] exchange (DM even lighter) ILD study: arXiv:2001.03011 consider very small mediator Phys. Rev. D 101, 075053 (2020) couplings to SM,Γ Γ SM tot CLIC study: arXiv:2103.06006 \Experimental" approach (model-independent) ) focus on cross section limits as a function of mediator mass and width A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 7 / 16 Analysis framework Simulating mono-photon events Dedicated simulation procedure for Whizard, with all \detectable" photons generated on Matrix Element level, matched with soft ISR. For details: J. Kalinowski et al., Eur. Phys. J. C 80 (2020) 634, arXiv:2004.14486 p Two variables, calculated separately Detector acceptance s = 500 GeV for each emitted photon: 102 θγ [GeV] p + q = 4E E · sin ; q − 0 γ 2 θ p γ 10 q = 4E E · cos ; γ + 0 γ BeamCal (E >30 GeV) 2 γ LumiCal (E >10 GeV) γ Tracking (E >5 GeV) are used to separate \soft ISR" ME photon cut 1 Hard photon cut γ p =0.1, 1, 10, 100 GeV emission region from the region T described by ME calculations. 1 10 102 q- [GeV] A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 8 / 16 Analysis framework Event selection Delphes framework used for detector simulation and event reconstruction. On generator level: Require: 1, 2 or 3 ME photons single photon with nonradiative events for signal γ p > 3 GeV & jηγj < 2:8 (ILC) only (for normalisation) T γ γ pT > 10 GeV & jη j < 2:6 (CLIC) all ME photons with q > 1 GeV & E γ > 1 GeV no other activity in the detector ± other reconstructed objects rejected are events with no electrons γ q± > 1 GeV & E > 1 GeV no LumiCal photons for any of the ISR photons no BeamCal photons no jets at least one ME photon with γ ◦ γ ◦ pT > 2 GeV & 5 < θ < 175 (ILC 500 GeV) γ ◦ γ ◦ pT > 5 GeV & 7 < θ < 173 (CLIC 3 TeV) A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 9 / 16 Analysis framework Background distributions For mono-photon events, two SM backgrounds are relevant: (radiative) Bhabha scattering and (radiative) neutrino pair production Two variables fully describe mono-photon event kinematics γ ) use 2D distribution of (pT , ηγ) to constrain DM production γ γ η η 2 2 1 104 1 105 0 0 3 −1 −1 10 − 2 −2 104 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 γ γ log p /pmin log p /pmin ILC 500 GeV X T T CLIC 3 TeV X T T (-80%/+30%) 1600 fb−1 (+80%) 1000 fb−1 A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 10 / 16 Analysis framework Signal distributions Simplified DM model used to simulate DM pair-production (see backup) Expected mono-photon distribution for fermion DM withM χ = 50 GeV and vector mediator of 400 GeV @ ILC 2.4 TeV @ CLICΓ =M = 0:03 γ γ η 10 η 2 2 1 1 1 1 0 0 10−1 −1 − −1 10 1 − 2 −2 − 10 2 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 γ γ log p /pmin log p /pmin X T T X T T Signal normalised to unpolarised DM pair-production cross section of 1 fb A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 11 / 16 Results Cross section limits for radiative events (with tagged photon) Vector mediator with Γ/M = 3% ILC @ 500 GeV CLIC @ 3 TeV -1 LR 1600 fb neg 4000 fb-1 -1 [fb] RL 1600 fb [fb] γ 10 γ pos 1000 fb-1 χ -1 χ χ RR 400 fb χ → -1 → - LL 400 fb - combined e e + + e 95%CL e 95%CL σ σ 1 1 102 103 102 103 104 MY [GeV] MY [GeV] Limits calculated with CLs approach using RooFit v3.60 A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 12 / 16 Results Cross section limits for total DM production cross section Corrected for probability of hard photon tagging! see backup slides Combined limits for mediator with Γ/M = 3% ILC @ 500 GeV CLIC @ 3 TeV Γ/m = 0.5 Γ/m = 0.5 2 [fb] Γ/m = 0.1 [fb] 10 Γ/m = 0.1 χ χ χ 2 Γ/m = 0.03 χ Γ/m = 0.03 → 10 → - - e Γ e Γ + /m = 0.01 + /m = 0.01 e 95%CL e 95%CL σ σ 10 10 102 103 102 103 104 MY [GeV] MY [GeV] p Radiation suppressed for narrow mediator with MY ∼ s ) weaker limits A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 13 / 16 Results Impact of systematic uncertainties following ILD study: Phys. Rev. D 101, 075053 (2020), arXiv:2001.03011 Cross section limits for mediator with Γ/M = 3% ILC @ 500 GeV CLIC @ 3 TeV RL (stat) pos (stat) 2 [fb] 2 RL (stat+sys) [fb] 10 pos (stat+sys) χ 10 χ χ χ H-20 (stat) combined (stat) → → - - e e + H-20 (stat+sys) + combined (stat+sys) e 95%CL e 95%CL σ σ 10 10 102 103 102 103 104 MY [GeV] MY [GeV] p Influence of systematic effects reduced for light mediators, MY < s A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 14 / 16 Results Coupling limits with systematic uncertainties Combined coupling limits for assumed mass and width of the mediator. ILC @ 500 GeV CLIC @ 3 TeV Γ/m = 0.5 Vector Γ/m = 0.1 Scalar 10−1 Γ/m = 0.03 1 Pseudoscalar Γ/m = 0.01 Axial-vector (95%CL) eeY −1 g −2 10 10 (95%CL limit) eeY g −2 − 10 10 3 102 103 102 103 104 MY [GeV] MY [GeV] Almost uniform sensitivity to geeY up to kinematic limit. Coupling limits weakly dependent on the assumed coupling structure! A.F.Zarnecki_ (University of Warsaw) DM searches with mono-photons April 14, 2021 15 / 16 Results Coupling limits with systematic uncertainties Combined coupling limits for assumed mass and width of the mediator. ILC @ 500 GeV CLIC @ 3 TeV Γ/m = 0.5 Vector Γ/m = 0.1 Scalar 10−1 Γ/m = 0.03 1 Pseudoscalar Γ/m = 0.01 Axial-vector (95%CL) Y χ χ −1 −2 g 10 10 (95%CL limit) Y χ eeY χ g g −2 −3 10 10 eeY g 102 103 102 103 104 MY [GeV] MY [GeV] Almost uniform sensitivity to geeY up to kinematic limit.