New signatures in directional dark matter searches in the lab Bradley J. Kavanagh (IPhT - CEA/Saclay) ICAP@IAP - 25th June 2015 Based on arXiv:1505.07406 NewDark
Overview Directional searches for DM in the lab: • Why search for a directional signal? • The signal • The experiments New signatures [arXiv:1505.07406] : • Non-relativistic DM-nucleon interactions ( very briefly! ) • The new signals • Discovery potential Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Directional detection Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Direct detection m χ Zoom in m N (slightly) ~ v ~ q Look for interactions of DM particles from the halo with nuclei in a detector - measure energy of the recoiling nucleus: • Expect low event rate —> build large detectors • Expect low energy events O(keV) —> low thresholds • Expect lots of backgrounds —> underground, radiopure materials, background discrimination - can be… problematic Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
The WIMP Wind WIMP: Weakly Interacting In the halo: Massive Particle v sun ∼ 220 km s − 1 Cygnus constellation v DM ∼ 220 km s − 1 Detector In the lab: ‘WIMP wind from Cygnus’ Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
The Smoking Gun Aim to measure the energy and direction of the recoiling nucleus. Cygnus WIMP signal Backgrounds Only need around 10 events to distinguish signal from background, and around 30 events to confirm the median direction of the flux [astro-ph/0408047,1002.2717] . Can also exploit time-dependence of the signal due to the motion of the Earth around the Sun [1205.2333] . Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Directional detection - TPCs Most advanced technology is the gaseous Time Projection Chamber (TPC) : [e.g. DRIFT, MIMAC, DMTPC, NEWAGE, D3] CF 4 gas - + E-field Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Directional detection - TPCs Most advanced technology is the gaseous Time Projection Chamber (TPC): [e.g. DRIFT, MIMAC, DMTPC, NEWAGE, D3] CF 4 gas - + E-field Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Directional detection - TPCs Most advanced technology is the gaseous Time Projection Chamber (TPC): [e.g. DRIFT, MIMAC, DMTPC, NEWAGE, D3] CF 4 gas - + E-field e Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Directional detection - TPCs Most advanced technology is the gaseous Time Projection Chamber (TPC): [e.g. DRIFT, MIMAC, DMTPC, NEWAGE, D3] CF 4 gas - + E-field e Get x,y of track from distribution of electrons hitting anode Get z of track from timing of electrons hitting anode Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
A ‘Real’ Signal Deaconu et al. (DMTPC, 2015) • Finite angular resolution - ∆ θ ∼ 20 � − 80 � • May not get full 3-D track information • May not get head-tail discrimination Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Dark Matter Signatures Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
DM-nucleon interactions Need to assume a particular interaction between DM and nucleons. ( v ∼ 220 km s − 1 ∼ 10 − 3 c) DM speed highly non-relativistic so consider (contact) operators which are zeroth order in and . v q Spin-independent (SI) coupling of DM and nucleon densities: O SI = 1 Spin-dependent (SD) coupling of DM and nucleon spins: O SD = S χ · S N Interaction cross-sections roughly independent of and . v q Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Non-relativistic effective operators Try to be as general as possible. Not all relativistic theories give rise to and . Consider operators higher order in O SI O SD and . [1203.3542] v q Some examples (you don’t want to see the whole list…): O 7 = ~ σ 7 ∼ v 2 S n · ~ v ⊥ ⊥ q ~ q ~ σ 15 ∼ q 4 ( q 2 + v 2 O 15 = − ( ~ )(( ~ ⊥ ) v ⊥ ) · ) S χ · S n × ~ m n m n DM speed appears as transverse speed, which is Hermitian: ~ q ~ v ⊥ = ~ v + ⇒ ~ v ⊥ · ~ q = 0 2 µ χ n Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Directional Signals Consider recoil rate as a function of recoil angle, , with θ = 0 θ pointing away from Cygnus: Recoil rate (normalised to a single event) Standard SI/SD int. σ ∼ q 0 v 0 Recoils away Recoils towards from Cygnus Cygnus Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Directional Signals Consider recoil rate as a function of recoil angle, , with θ = 0 θ pointing away from Cygnus: σ ∼ q 4 ( q 2 + v 2 ⊥ ) Recoil rate (normalised to a single event) σ ∼ v 2 ⊥ Recoils away Recoils towards from Cygnus Cygnus Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Comparing operators Standard signal Signal due to O 7 Signal due to O 15 Can we distinguish these different operators? Need to perform a full likelihood analysis… Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Distinguishing operators: Energy-only σ SI ∼ q 0 v 0 How many events are required to reject σ 7 ∼ v 2 ‘standard’ SI/SD interactions? ⊥ σ 15 ∼ q 4 ( q 2 + v 2 ⊥ ) MENTION THAT THIS IS ENERGY-ONLY Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Comparing energy spectra σ SI ∼ q 0 v 0 σ 7 ∼ v 2 ⊥ σ 15 ∼ q 4 ( q 2 + v 2 ⊥ ) Energy spectra for and are indistinguishable : O 7 O 4 Forward recoils are suppressed, but transverse recoils are enhanced. For slowly varying distributions, these two effects roughly cancel. Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Distinguishing operators: Energy + Directionality σ SI ∼ q 0 v 0 How many events are required to reject σ 7 ∼ v 2 ‘standard’ SI/SD interactions? ⊥ σ 15 ∼ q 4 ( q 2 + v 2 ⊥ ) Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Conclusions Need to be careful to include detector uncertainties, as well as astrophysical uncertainties, but we can say: • NR operators lead to new directional signatures: • Operators coupling to lead to more directional rates q 2 v 2 • Operators coupling to lead to more isotropic rates ⊥ • With events it should be possible to O (100 − 500) distinguish NREFT operators from standard operators at the level (may not be possible in energy-only 2 σ experiments) Directional detection allows us to probe otherwise inaccessible particle physics of Dark Matter! Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Conclusions Need to be careful to include detector uncertainties, as well as astrophysical uncertainties, but we can say: • NR operators lead to new directional signatures: • Operators coupling to lead to more directional rates q 2 v 2 • Operators coupling to lead to more isotropic rates ⊥ • With events it should be possible to O (100 − 500) distinguish NREFT operators from standard operators at the level (may not be possible in energy-only 2 σ experiments) Directional detection allows us to probe otherwise inaccessible particle physics of Dark Matter! Thank you Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Back-up slides Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
A Real TPC DRIFT-IIe prototype detector @ Occidental College, LA Two back-to-back TPCs Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
A Real TPC DRIFT-IIe prototype detector @ Occidental College, LA Anode Cathode Two back-to-back TPCs Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
Consequences for relativistic theories Many ‘dictionaries’ are available which allow us to translate from relativistic interactions to NREFT interactions [e.g. 1211.2818, 1307.5955, 1505.03117] h L 1 i = 4 m χ m n O 1 L 1 = ¯ χχ ¯ nn ⇒ h |M| 2 i ⇠ F M ( q 2 ) → χγ µ γ 5 χ ¯ h L 6 i = 8 m χ ( m n O 8 + O 9 ) L 6 = ¯ ⇒ n γ µ n h |M| 2 i ⇠ v 2 ⊥ F M ( q 2 ) → These two relativistic operators cannot be distinguished without directional detection. Bradley J Kavanagh (IPhT - CEA/Saclay) Directional searches for DM ICAP@IAP - 25th June 2015
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