Direct Detection and Collider Searches of Dark Matter Lecture 2 - PowerPoint PPT Presentation

Direct Detection and Collider Searches of Dark Matter Lecture 2 Graciela Gelmini - UCLA Dark Matter School, Lund, Sept. 26-30, 2016

Graciela Gelmini-UCLA Content of Lecture 2 • Introduction to WIMP dark matter searches, direct detection world wide efforts. • Main elements of the expected event rate in direct detection experiments: detector response, cross section and halo model • Uncertainties related to detector response and particle DM physics • Uncertainties related to DM particle physics Subject is very vast, so idiosyncratic choice of subjects + citations disclaimer Dark Matter School, Lund, Sept. 26-30, 2016 1

Graciela Gelmini-UCLA . WIMP DM searches Direct detection world-wide efforts Dark Matter School, Lund, Sept. 26-30, 2016 2

Graciela Gelmini-UCLA WIMP DM searches: • Direct Detection- looks for energy deposited within a detector by the DM particles in the Dark Halo of the Milky Way. Could detect even the DM interaction might be too weak to detect) • Indirect Detection- looks for WIMP annihilation • At colliders (the LHC) as missing transverse energy, mono-jet or mono-photon events (Caveat: the DM mass may be above 2 TeV or its signature hidden by backgrounds) All three are independent and complementary to each other! Even if the Large Hadron Collider finds a DM candidate, in order to prove that it is the DM we will need to find it where the DM is, in the haloes of our galaxy and other galaxies. Dark Matter School, Lund, Sept. 26-30, 2016 3 a very subdominant WIMP component. (Caveat: (or decay) products. (Caveat: the DM may not annihilate or decay)

Graciela Gelmini-UCLA Milky Way’s Dark Halo Fig. from L.Baudis; Klypin, Zhao and Somerville 2002 The Sun moves in the Dark Halo of our Galaxy. We have DM “wind” on Earth. Dark Matter School, Lund, Sept. 26-30, 2016 4 10 7 (GeV/ 𝑛 𝜓 ) WIMP’s passing through us per cm 2 per second! ( ∗ See exercise)

Graciela Gelmini-UCLA requires constant fight against backgrounds, Dark Matter School, Lund, Sept. 26-30, 2016 recoil direction) of the Earth around the Sun (few % effect) rays. Direct DM Searches: must be underground to shield from cosmic section, dark halo model, nuclear form the detector which recoils • WIMP typically interacts with a nucleus in 5 • Small E 𝑆𝑓𝑑𝑝𝑗𝑚 ≤ 50 keV(m/100 GeV) • Rate: depends on WIMP mass, cross factors... typical... < 1 event/ 100 kg/day • Annual rate modulation due to the rotation • Most searches are non-directional but some in development are (try to measure the

Graciela Gelmini-UCLA Direct DM Searches: Many experiments! in mines (Soudan, Boulby, Kamioka) or mountain tunnels (Gran Sasso, Modane, YangYang, Jin-Ping) Dark Matter School, Lund, Sept. 26-30, 2016 6

Graciela Gelmini-UCLA Sensitivity: Dark Matter School, Lund, Sept. 26-30, 2016 7

Graciela Gelmini-UCLA Sensitivity: Dark Matter School, Lund, Sept. 26-30, 2016 8

Graciela Gelmini-UCLA Backgrounds in Direct DM detectors: Everything is radioactive! Some examples: neutrons, the soil contains 1 - 3 mg of U per kg) So, no bananas in the lab! Dark Matter School, Lund, Sept. 26-30, 2016 9 - In your body 4000 14 C decay/s and 4000 40 K decays/s (e − , 𝛿 , 𝜉 𝑓 ), - 7000 radon atoms escape of the ground per m 2 per s, - There are 10 7 plutonium atoms in1 kg of soil (from transmutation of 238 U by fast cosmic ray

Graciela Gelmini-UCLA Backgrounds in Direct DM detectors: - 1- Radioactivity of surroundings gammas and neutrons, radon decay in the air) require either passive shields: Pb against the gammas, polyethylene/water against neutrons or active shields: large water Cherenkov detectors or scintillators for gammas and neutrons Fig. from L. Baudis- Right: XMASS (Xe at Kamioka, Japan) Dark Matter School, Lund, Sept. 26-30, 2016 10 Natural radioactivity of 238 U, 238 Th, 40 K decays in rock and walls of the laboratory produce mostly

Graciela Gelmini-UCLA Backgrounds in Direct DM detectors: -2- Internal radioactivity of detector and shield materials Many strategies to use material with very low radioactivity. E.g. ultra-pure Ge spectrometers are used to screen the materials before using them in a detector, down to ≤ parts-per-billion (ppb) levels - 3- Cosmic rays and secondary reactions Must go underground. Dark Matter School, Lund, Sept. 26-30, 2016 11

Graciela Gelmini-UCLA Signal in Direct Searches: Fig. from D. Akerib Dark Matter School, Lund, Sept. 26-30, 2016 12

Graciela Gelmini-UCLA Signal in Direct Searches: (In red: had signal claims) Dark Matter School, Lund, Sept. 26-30, 2016 𝑟 , not well developed yet ⃗ measure recoil -Ionization + Scintillation(Xe, Ar, Ne): XENON, LUX, PandaX, DarkSide, ArDM -Ionization + Phonons (Ge, Si): CDMS, SuperCDMS, EDELWEISS, EURECA? (Xe, Ar, Ne are Liquid/Gas Detectors- others are crystals (superheated bubble chamber, bubbles of C 4 F 1 0 ) -Threshold detectors: PICASSO, SIMPLE, COUPP, PICO -Phonons (Ge, Si, Al 2 O 3 , TeO 2 ): (CRESST-I) , Cuoricino, CUORE SABRE // DEAP, MiniCLEAN, XMASS, -Ionization (Ge, Si): CDEX, DAMIC, CoGeNT, C4 • Single Channel Techniques: 13 -Scintillation (NaI, CsI // single phase noble-gas): DAMA/LIBRA, ANAIS, DM-Ice, KIMS, • Hybrid detector techniques for discrimination: -Scintillation + Phonons (CaWO 4 , Al 2 O 3 ): CREST-II, EURECA? • Directional low density gas TPCs(CS 2 , CF 4 ): DRIFT, DM-TPC, MIMAC,

Graciela Gelmini-UCLA Example: Noble Liquid detectors: Either single phase (scintillation) or double phase (ionization/ scintillation) act as their own veto, up-scalable to multi-tonnes • Single-Phase: Scintillation XMASS (Xe,Japan, Kamioka), DEAP/ MiniCLEAN (Ar/Ne,US/Canada, SNOLab) (one delayed) XENON1T/nT (Xe, US/Switzerland/Germany/France/Portugal/Italy/Japan/China, LNGS), LUX/LZ (Xe, US/UK, Sanford Lab), DarkSide (Ar, US/Europe, LNGS), WARP (Ar, Italy/US, LNGS), ZEPLIN (Xe, UK/US, Boulby), ArDM (Ar, Switzerland/Spain/UK, Canfranc) Dark Matter School, Lund, Sept. 26-30, 2016 14 • Two-phase liquid and gas: Scintillation and ionization seen as light pulses

Graciela Gelmini-UCLA Example of two-phase Xe: LUX Actual data: neutral recoils expected in red band (evens compatible with backgrounds). Dark Matter School, Lund, Sept. 26-30, 2016 15 𝑇 2 /𝑇 1 versus 𝑇 1 plots. Calibration data and actual data (2013)

Graciela Gelmini-UCLA Example: CDMS and SuperCDMS (Ge and Si crystals) “Ionization yield” = 1 Calibration data. Dark Matter School, Lund, Sept. 26-30, 2016 16 - DM particles and neutrons produce nuclear recoils: only a fraction 𝑅 of energy deposited in a nucleus goes into ionization ( 𝑅 is called “quenching factor”) 𝑅 𝐻𝑓 ≃ 0.3 , 𝑅 𝑇𝑗 ≃ 0.25 , bulk goes into phonons, thus “Ionization yield” = 𝑅 - Photons interact with electrons: All energy deposited into electrons goes into ionization:

Graciela Gelmini-UCLA CDMS-II three candidate events in Si Data taken from July 2007 to Sep.2008- results published in 2013 Dark Matter School, Lund, Sept. 26-30, 2016 17

Graciela Gelmini-UCLA Directional detectors: low density gas TPCs DRIFT at Boulby (CS 2 ) and DM-TPC at MIT-WIPP (CF 4 ) Measure direction of recoil- track reconstructed through drift of e Dark Matter School, Lund, Sept. 26-30, 2016 18

Graciela Gelmini-UCLA 160 Dark Matter School, Lund, Sept. 26-30, 2016 form factor (this is a charge form factor, i.e. for p, assumed to hold also for n), For larger 𝑟 the loss of coherence is taken into account with a nuclear form factor and WIMPs interact coherently with all the nucleons in a pointlike nucleus. 𝑛 𝜓 𝑛 ≥ GeV WIMPs interact coherently with nuclei 𝐵 1/3 � ( ∗ ) 𝑝𝑠 𝑟 is the momentum transfer and 𝑟 = | ⃗ 𝑟 , where ⃗ 19 𝑟| , is 1 WIMPs are not relativistic, 𝑤 ≃ 300 km/s ≃ 10 −3 the de Broglie wavelength of the mediator, 1 𝑟 > 𝑆 𝑂𝑣𝑑𝑚𝑓𝑣𝑡 ≃ 1.25 𝑔𝑛 𝐵 1/3 𝑟 < 𝑁𝑓𝑊 � ( ∗ You will prove this in an exercise) (1= 197 MeV fm; 1 femtometre, fm (or Fermi) = 10 −15 m) e.g. for 𝑛 << 𝑁 𝑟 ≃ 𝑁𝑓𝑊 � 𝐻𝑓𝑊 � 𝐺(𝐹) = ∫ 𝑓 −𝑗𝑟𝑠 𝜍 𝑂𝑣𝑑𝑚𝑓𝑝𝑜 (𝑠)𝑒𝑠 . For Spin-Independent interactions one uses conventional the Helmi 𝐺(𝐹) = 3𝑓 −𝑟2𝑡2/2 [𝑡𝑗𝑜(𝑟𝑒) − 𝑟𝑒 𝑑𝑝𝑡(𝑟𝑒)]/(𝑟𝑒) 3 , with 𝑡 = 1 fm, 𝑒 = √𝑆 2 − 5𝑡 2 , 𝑆 = 𝑆 𝑂𝑣𝑑𝑚𝑓𝑣𝑡 ≃ 1.2𝐵 1/3 fm, 𝑟 = √2𝑁𝐹 .

Graciela Gelmini-UCLA Caveat: Sub-GeV “Light Dark Matter” (LDM) Dark Matter School, Lund, Sept. 26-30, 2016 0712.0562; Kopp et al. 0907.3159; Essig, Mardon & Volansky, 1108.5383; Essig et al. 1206.2644; Batell, Essig & Surujon 1406.2698 Bernabei et al. (electron ionization, electronic excitation, molecular dissociation...) but LDM could deposit enough energy, 1 to 10 eV, interacting with electrons ( ∗ ) � 𝑁 10𝐻𝑓𝑊 � 2 𝑛 𝑛𝑏𝑦 𝐹 𝑓𝑚𝑏𝑡𝑢𝑗𝑑−𝑂𝑣𝑑𝑚𝑓𝑗 𝑛 ≃ keV to 0.1GeV << 𝑁 , thus the maximum energy imparted in an elastic collision with the 20 whole nucleus is below threshold for most experiments ( 𝐹 𝑢ℎ𝑠𝑓𝑡 > 0.1 keV) ≃ 20𝑓𝑊 � 100𝑁𝑓𝑊 � ( ∗ You will prove this in an exercise)