DUNE BSM Group Meeting, April 10 th , 2018 In collaboration with KC - PowerPoint PPT Presentation

Doojin Kim DUNE BSM Group Meeting, April 10 th , 2018 In collaboration with KC Kong, Jong-Chul Park and Seodong Shin

Summary: Generic BDM Signatures ( 𝑏 ) Elastic scattering (eBDM) (cf. eBDM at DUNE [Necib, Moon, Wongjirad, Conrad ( 2016 ); Alhazmi, Kong, Mohlabeng, Park ( 2016 )] ) ProtoDUNE 𝜓 1 𝜓 1 𝑛 0 = 𝐹 1 = ~30 MeV −~10 GeV 𝜓 1 = ~10 −1 − 10 −6 cm −2 s −1 with ℱ 𝛿 1 𝜚 Today’s focus (in collaboration with 𝑓/𝑂 𝑓/𝑂 𝜓 0 𝜓 1 Kong, Park and Shin) 𝜓 0 𝜓 1 ( 𝑐 ) Inelastic scattering ( i BDM) (cf. i BDM at DUNE [ DK , Park, Shin ( 2016 )] ) ProtoDUNE 𝜓 1 𝜓 2 𝜓 1 Galactic Center 𝛿 1 𝜚 𝑓/𝑂 • 𝜓 0 : heavier DM 𝑓/𝑂 (in)visible • 𝜓 1 : lighter DM • 𝛿 1 : boost factor of 𝜓 1 • 𝜓 2 : massive unstable dark-sector state Studied in arXiv: 1803.03264 in collaboration with Chatterjee et al. • 𝜚 : mediator/portal particle -1- Doojin Kim, CERN DUNE BSM Group Meeting

Summary: Production of BDM & Benchmark Model  Production of boosted DM: two-component boosted DM scenario [Agashe, Cui, Necib, Thaler ( 2014 )] ℒ int ∋ − 𝜗 𝜈𝜉 𝑌 𝜈𝜉 + 𝑕 11 𝜓 1 𝛿 𝜈 𝜓 1 𝑌 𝜈 + 𝑕 12 𝜓 2 𝛿 𝜈 𝜓 1 𝑌 𝜈 + h. c. +(others) 2 𝐺  Vector portal (e.g., dark gauge boson scenario) [Holdom ( 1986 )] 𝛿 𝑌  Dark SM  Fermionic DM 𝜗  𝜓 2 : a heavier (unstable) dark-sector state 𝜓 2 Flavor-conserving neutral current  elastic scattering  𝑌  𝑕 12 Flavor-changing neutral current  inelastic scattering   Not restricted to this model: various models conceiving BDM signatures 𝜓 1  BDM source: galactic center, solar capture, dwarf galaxies, assisted freeze-out, semi-annihilation, fast- moving DM etc. [Agashe et al. ( 2014 ); Berger et al. ( 2015 ); Kong et al. ( 2015 ); Alhazmi et al. ( 2017 ); Super-K ( 2017 ); Belanger et al. ( 2011 ); D’Eramo et al. ( 2010 ); Huang et al. ( 2013 )]  Portal: vector portal, scalar portal, etc.  DM spin: fermionic DM, scalar DM, etc.  iBDM-inducing operator: two chiral fermions, two real scalars, dipole moment interactions, etc. [Tucker- Smith, Weiner ( 2001 ); Giudice, DK , Park, Shin ( 2017 )] -2- Doojin Kim, CERN DUNE BSM Group Meeting

Challenge: Cosmic-origin BGs and eBDM Signal Signal of interest Cosmogenic neutrons (very rare) Quite a few low-energy particles 𝑓 − Vertical muons Atmospheric above 10 MeV: ~𝟐𝟏 𝟐𝟏 / 𝐧 𝟑 /yr neutrinos (very 𝑓 − rare): ~𝟓𝟏 single- track-involving e - like events/yr/kt 𝑓 − An impractically Fiducial vol. small mistake rate Total vol. Active vol. is demanded! irreducible Insulator Exoskeleton -3- Doojin Kim, CERN DUNE BSM Group Meeting

“Earth Shielding”  Accept only events Cosmic muons Boosted DM traveling through the earth (i.e., coming out of  Background and signal the bottom surface) at the events are coming from price of half statistics; everywhere. direction inferred from  Half of them travel recoil track  Essentially no through the earth. cosmic-origin BGs except Earth atmospheric neutrino  Backgrounds can’t background (cf. observation penetrate the earth while of upward-muons induced by signals can! muon neutrinos created by DM annihilation [NOvA Collaboration in progress] ) -4- Doojin Kim, CERN DUNE BSM Group Meeting

Muon Flux inside the Earth 𝜈 at sea level is ~100 m −2 s −1 sr −1 = 3 ×  𝑂 10 9 m −2 yr −1 sr −1 . [Particle Data Group ( 2015 )]  𝑂 𝜈 at 20 km.w.e. ≈ 7 km below sea level is ~10 −9 m −2 s −1 sr −1 , i.e., suppressed by a factor of ~10 11 .  (Potential) muon- induced BG is negligible for muons incident at 𝜄 > 𝜄 𝑑𝑠 . 𝜄 𝑑𝑠 𝜄 𝑑𝑠 ≈ 7 km ≈ 0.03 ∘ 2𝑆 ⨁ 𝑆 ⨁ 2𝜄 𝑑𝑠 [Particle Data Group ( 2015 )] Flattened by neutrino-genic muons -5- Doojin Kim, CERN DUNE BSM Group Meeting

Situation with 1 - yr Data Collection from “All” Sky 𝝍 𝟐 𝝃 𝜓 1 ~ 3 × (10 1 − 10 6 ) 40 ~ 2 neutrino-induced e -like, cm −2 yr −1 ℱ 2 single-track events/yr/kt Effectively, half year -6- Doojin Kim, CERN DUNE BSM Group Meeting

Improving Signal Sensitivities  The neutrino flux is uniformly distributed, whereas the boosted DM flux is mostly coming from the Galactic Center!  An angle cut improves! [Necib, Moon, Wongjirad, Conrad ( 2016 ); Super-K ( 2017 )] 𝜄 𝐷  What value of 𝜄 𝐷 is the best/most optimal choice? -7- Doojin Kim, CERN DUNE BSM Group Meeting

Angular Cut to Maximize the Signal Sensitivity  Various significance calculation methods are considered since # of expected BG events are small.  Comparison of different signal events for a  Comparison of different exposure times for fixed number of BG events a fixed model point  A larger angle cut is better if # of signal is  A larger angle cut is better if more data is bigger. collected. -8- Doojin Kim, CERN DUNE BSM Group Meeting

Model-independent Sensitivity  Number of signal events 𝑂 sig is 𝑂 sig = 𝜏 𝜗 ∙ ℱ ∙ 𝑢 exp ⋅ 𝑂 𝑓  𝜏 𝜗 : scattering cross section between 𝜓 1 and (target) electron  ℱ : flux of incoming (boosted) 𝜓 1  𝑢 exp : exposure time Controllable! (once a detector is determined)  𝑂 𝑓 : total # of target electrons Realistic experimental effects such as cuts, energy threshold, etc are absorbed into 𝜏 𝜗 . -9- Doojin Kim, CERN DUNE BSM Group Meeting

More Familiar Form  More familiar parameterization possible with the below modification! 90 % C.L. 𝜏 𝜗 vs. 𝑛 0 (just like 𝜏 vs. 𝑛 DM in conventional WIMP searches) -10- Doojin Kim, CERN DUNE BSM Group Meeting

Model-independent Sensitivity  1 -year exposure, i.e., effectively half-year data collection ( = 1.6 × 10 7 sec), is assumed.  The limits from all-sky data are DM halo model- independent (up to total flux).  Angular cuts improve the experimental sensitivities at the cost of DM halo model- dependence (optimal 𝜄 𝐷 values differ detector-by- detector & run time). -11- Doojin Kim, CERN DUNE BSM Group Meeting

Dark Photon Parameter Space: Invisible X Decay  Case study 1 : mass spectra for which dark photon decays Babar into DM pairs, i.e., 𝑛 𝑌 > 2𝑛 1  1 -year data collection from Inelastic scattering the entire sky and 𝑕 11 = 1 are assumed.  Elastic and inelastic scattering channels are complementary to each Elastic scattering other. -12- Doojin Kim, CERN DUNE BSM Group Meeting

Dark Photon Parameter Space: Visible X decay  Case study 2 : mass spectra for which dark photon decays NA 48 / 2 Babar into lepton pairs, i.e., 𝑛 𝑌 < 2𝑛 1  1 -year data collection from Inelastic scattering the entire sky and 𝑕 11 = 1 are assumed.  Elastic scattering channel allows us to explore (slightly) wider parameter space (for Elastic scattering the chosen benchmark point). -13- Doojin Kim, CERN DUNE BSM Group Meeting

Expected Number of Signal Events  Full ProtoDUNE and 2𝑛 1 > 𝑛 𝑌 (i.e., the case of visibly-decaying X) and 𝑕 11 = 1 are assumed.  Shown are the results with 1 -year (effectively ½ -year) exposure. SK 30 ∘ – cone 90% C.L. from a BDM search SK all-sky 90% C.L. from SK all-sky 90% C.L. from atm- 𝜉 measurements atm- 𝜉 measurements ProtoDUNE can cover the parameter space uncovered by SK! (especially the region where the relevant recoil energy is lower than 100 MeV.) -14- Doojin Kim, CERN DUNE BSM Group Meeting

Expected Experimental Reach  Full ProtoDUNE and 2𝑛 1 > 𝑛 𝑌 (i.e., the case of visibly-decaying X) and 𝑕 11 = 1 are assumed.  Shown are the results with 1 -year and 2 -year exposures. SK 30 ∘ – cone 90% C.L. from a BDM search SK all-sky 90% C.L. from SK all-sky 90% C.L. from atm- 𝜉 measurements atm- 𝜉 measurements The analysis with an angle cut allows to probe more parameter space , as expected. -15- Doojin Kim, CERN DUNE BSM Group Meeting

Conclusions 𝑤 𝐸𝑁 Non-relativistic Relativistic Scattering ( 𝑤 𝐸𝑁 ≪ 𝑑 ) ( 𝑤 𝐸𝑁 ~𝑑 ) elastic Direct detection Boosted DM (eBDM) in elastic inelastic DM (iDM) inelastic BDM ( 𝑗 BDM)  Overwhelming cosmic-ray background can be controlled with the “ Earth Shielding ”.  ProtoDUNE possesses excellent sensitivities to a wide range of (light) boosted DM, hence allows a deeper understanding in non-minimal dark sector physics.  ProtoDUNE can provide an alternative avenue to probe dark photon parameter space and information complementary to that from i BDM searches.  Physics at ProtoDUNE can offer a more realistic BSM physics guideline for DUNE . -16- Doojin Kim, CERN DUNE BSM Group Meeting

i BDM and eBDM Prospects at DUNE  Comparison between ProtoDUNE 1 -year vs. DUNE 10 kt + 10 kt, DUNE 20 kt + 20 kt 1 -year with all-sky data for i BDM (left panel) and eBDM (right panel) signatures  The limit for i BDM (eBDM) becomes lower by ~2 ( ~1 ) orders of magnitude at DUNE due to background-free analysis (large neutrino-induced background).  Improvement by 𝑊 Detector for iBDM vs. 𝑊 Detector for eBDM. -17- Doojin Kim, CERN DUNE BSM Group Meeting