Acknowledgements: Contact email: schakdar@holycross.edu This research work is supported by the College of the Holy Cross’s Bachelor Ford Summer Fellowship 2020 References: 1. P.Q Hung, Phys. Lett. B649 (2007) 275279, arXiv: 0612004 2. S. Chakdar, K. Ghosh, V. Hoang, P. Q. Hung and S. Nandi, Phys. Rev. D95 no. 1, (2017) 015014, arXiv:1606.08502 3. S. Chakdar, K. Ghosh, V. Hoang, P.Q Hung and S. Nandi, Phys.Rev.D 93 (2016) 3, 035007, arXiv: 1508.07318 Particle Content Prospect of singlet scalar DM candidate in the EW scale-!" model Shreyashi Chakdar1, Dilip Ghosh2, P. Q. Hung 3, and Najimuddin Khan2, 1 College of the Holy Cross, 2Indian Association for the Cultivation of Science, 3University of Virginia Neutrino mass is the only evidence of BSM Physics so far! • Neutrino (ν) masses → popular “Seesaw mechanism” • In general Seesaw Mechanism: #$ →&' 2 )×' 1 , singlet • RH neutrino mass at GUT scale! NOT directly testable at LHC • Stand scenes: L-R : mD ~ Λ EW , MR ~MWR , GUT: MR ~ Λ GUT #$’s are Sterile in standard scenarios • What if MR ~ Λ EW? Can #$ ’s be non-sterile? Solution: • SM + Mirror Fermions + extended scalar sector Gauge Group : SU(3)c x SU(2)W x U(1)Y • . = 0 12 3 14 3 5678 92= 1 (custodial global symmetry SU(2)) • #1~ : (Λ=>) →A “large” triplet vev spoils . = 1 at Tree level • To restore the Custodial symmetry, a triplet Higgs scalar @ = (3, , 8 = 0) is added to the scalar sector such that • The Higgs potential has a global &' 2 ) × &' 2 $ symmetry →&' 2 D • The nature of EW symmetry breaking is intrinsically linked to Majorana mass of the non-sterile RH E • Physical scalars are grouped into Custodial SU(2)D states: 18 physical scalars grouped 5 + 3 + 3 + 3 + 3 + 1 Quintet →FG ±±, FG ±, FG I Triplet →FJ ±, FJ I, F′J ±, F′J I, F1 ±, F1 I , F1 L±, F1 LI Real Singlet →FM I, F′M I, FM1 I , FM1 LI , FMI, FM NI Complex Singlet →ON I Singlet States: Vev’s satisfy: • 6 mass eigenstates are denoted by P FQ, P F, RF’, RF’’, RF’’’, RF’’’’ • P FN →lightest (DM), next heavier ones are RF’, RF’’, RF’’’, with heaviest state RF’’’’ and RF →125 GeV • The pseudo singlet scalar is the DM candidate (Mev-GeV mass range) • The main contribution to the DM effective annihilation cross-section comes from annihilation channel ONI ONI →SM SM, (diagrams below) • Relic density related to annihilation cross-section and decay lifetime • Framework has Majorana and new mirror fermion masses within the reach of the current colliders • Complete scalar sector spectrum including heavier triplets, doublets and singlet Higgs states in conjunction with the current 125-GeV LHC data is analyzed • Prospect of the singlet scalar fulfilling the role of the DM candidate is investigated wrt the current bounds • EWE$ scenario links neutrino mass, DM studies and Long-lived Particles (LLP) searches at the Collider Extended Scalar sector Singlet Scalar • ONI = \∅NI^ , the complex singlet is investigated to be DM candidate in this analysis • At tree level, the mass of the complex singlet scalar ON I= \∅N I^ is given by • In gen, RFNI, F8 I, FM1 I , F81 I , FNI and FM I_ components can mix through • Two doublets in each sector, coupling to up and down components • Yukawa part of the Lagrangian is given by: Benchmark Points and experimental data Summary Dark Matter Model and Framework TABLE I: Branching Ratios for SM-like Higgs (`a ~ 125 GeV) decaying through various SM and BSM channels for a model Benchmark Point TABLE II: Signal Strengths for the Higgs-like Boson for the benchmark point examined in Table I MAs 0 <Mh/2 3 band in DMh2=0.1198±0.0026 MAs 0= 85 c (v1 + v2) (v1 M + v2 M) 1 0 As 0As 0 coupling: 4 a v1+2 5 c (v1 M+v2 M) 2 0 As 0As 0 coupling: 4 a v1+2 5 c (v1 M+v2 M) Allowed from Direct detection (Xenon 1T) 20 50 100 200 500 10-4 0.01 1 100 Mass of the Dark Matter MAs 0 (GeV) As 0h2 Fig: Plot shows variation of relic density (Ωℎ8) vs Dark matter mass. The red line signifies bounds coming from the recent direct detection xenon 1T data. The blue band