Antideuterons from Dark Matter and Hadronization Uncertainties - PowerPoint PPT Presentation

Antideuterons from Dark Matter and Hadronization Uncertainties Based on arXiv:1207.4560 [hep-ph], arXiv:1402.6259 [hep-ph] Lars A. Dal Department of Physics, University of Oslo From Higgs to Dark Matter 2014, Geilo 16.12.2014

Indirect DM Detection Dark matter couples weakly to ordinary matter by definition ⇒ Low decay/annihilation rate ⇒ Small cosmic ray signature Need particle channels where the signal is not drowned by background Neutral cosmic rays ( ν , γ ) Unaffected by Galactic magnetic fields. No deflection Background can be overcome by looking at DM rich targets Charged cosmic rays Diffusion thrugh turbulent magnetic fields. No directional information Low background is a must. Antimatter Indirect DM Detection Indirect DM Detection 2 / 13

Status: Positrons and Antiprotons 1 AMS-02 (2013) Fermi LAT (2011) PAMELA (2010) PAMELA (2009) AMS-01 (2007) HEAT (1997) Positron fraction e + /(e + + e − ) spallation model 0.1 0.01 1 10 100 1000 E [GeV] Large excess of positrons at high energies – pulsar source? No sign of an excess in the antiproton channel Logical next step? Antinuclei Indirect DM Detection Status: Positrons and Antiprotons 3 / 13

The Antideuteron Channel Lightest antinucleus: ¯ p ¯ n Low background at low energies from cosmic ray collisions on interstellar matter Duperray et al. , arXiv:astro-ph/0503544 Energy losses during propagation populate the spectrum at low energies. The picture after propagation is less extreme. Indirect DM Detection The Antideuteron Channel 4 / 13

Antideuteron detection The Past The Present The Future The BESS The AMS-02 experiment. The upcoming experiment. Currently collecting data onboard GAPS dedicated Current upper limit the ISS. antideuteron on the balloon antideuteron flux. experiment. Indirect DM Detection Antideuteron detection 5 / 13

Antideuteron Formation Formation of atomic nuclei not handled in Monte Carlos. Simple model: Coalescence Nucleons with ∆ p < p 0 coalesce to form a nucleus Additional condition: Close in position space – weakly decaying particles considered stable p 0 calibrated against experimental data, typically large spread in best fit p 0 -values between experiments and Monte Carlos p 0 ∼ 100 MeV � Λ QCD , highly sensitive to 2-particle correlations from hadronization Antideuteron Formation Antideuteron Formation 6 / 13

Hadronization and antideuterons My work: Estimate uncertainty from hadronization arXiv:1207.4560 [hep-ph] Comparison of antideuteron spectra generated with Herwig++ and Pythia Large discrepancies, especially at high and low energies Antideuteron Formation Hadronization and antideuterons 7 / 13

Tuning of Hadronization Models Several free parameters in hadronization models tuned to fit experimental data Not specifically tuned to produce correct (anti)nucleon spectra or 2-particle correlations My work: Tune 3 most important Herwig++ hadronization parameters + p 0 to reproduce experimenal antideuteron spectra arXiv:1402.6259 [hep-ph] Antideuteron data: ALEPH, ZEUS, CLEO, antiproton data: ALEPH, OPAL 10 9 Monte Carlo events required per parameter point. Challenging to find best fit point with finite CPU time Hadronization Tuning Tuning of Hadronization Models 8 / 13

Best Fit Parameters Some 40000 CPU core hours later... Uncertainty ( 1 σ ) ∗ Parameter Default value Best fit value + 6 . 2 p 0 [MeV] – 143.2 − 5 . 5 + 0 . 18 3.25 3.03 ClMaxLight − 0 . 15 + 0 . 19 1.20 1.31 PSplitLight − 0 . 32 + 0 . 15 0.49 0.48 PwtDIquark − 0 . 04 Best fit χ 2 / d . o . f = 10 . 6 / 14 . 2 Likelihood function in the parameters can be used to find uncertainty on antideuteron flux from tuned parameters ∗ Non-parabolic uncertainty calculated using the MINOS algorithm in Minuit Hadronization Tuning Best Fit Parameters 9 / 13

Application: Gravitino Dark Matter Gravitino: SUSY partner of the Graviton R-parity conservation: Gravitino LSP ”absolutely” stable R-parity violation (RPV): Gravitino is unstable but long-lived. ijk L i Q j ¯ ijk ¯ U i ¯ D j ¯ Operators of interest: λ ′ D k , λ ′′ D k U i ¯ ¯ D j ¯ D k operators allows decays into 3 antiquarks. Larger antideuteron yield than typical DM decays/annihilations (to q ¯ q ). d ∝ Γ ∝ λ 2 ; results can easily be re-scaled to any value of λ Φ ¯ Gravitino Dark Matter Application: Gravitino Dark Matter 10 / 13

Antideuteron Spectrum Near Earth Propagation: NFW DM density profile, ’med’ set of diffusion parameters G = 50 GeV, λ = 10 − 5 m ˜ BESS L 1 Q 1 ¯ D 2 10 − 4 U 1 ¯ ¯ D 1 ¯ D 2 Flux increases with increasing mass and Φ [(m 2 s sr GeV/n) − 1 ] AMS-02 AMS-02 10 − 5 RPV coupling Can set limits on mass 10 − 6 GAPS LDB+ and RPV coupling from 10 − 7 experiments 10 − 8 10 − 9 10 − 1 10 0 10 1 T [GeV/n] Gravitino Dark Matter Antideuteron Spectrum Near Earth 11 / 13

Limits on RPV couplings Prospective upper limits from GAPS 10 0 95% CL exclusion limits L 1 Q 3 ¯ D 3 10 − 1 assuming 0 observed L 1 Q 1 ¯ D 2 events 10 − 2 U 3 ¯ ¯ D 2 ¯ D 3 10 − 3 U 1 ¯ ¯ D 1 ¯ Factor 2 − 4 Stronger D 2 10 − 4 than existing limits on λ max RPV couplings 10 − 5 10 − 6 10 − 7 10 − 8 10 − 9 10 1 10 2 10 3 G [GeV] m ˜ Gravitino Dark Matter Limits on RPV couplings 12 / 13

Summary Antideuteron channel suitable for DM searches due to low background Antideuteron spectrum is highly sensitive to hadronization model, factor ∼ 3 difference between Herwig++ and Pythia Tuning necessary for giving a consistent description Uncertainty from tuned parameters of factor < 2 after re-tuning Antideuterons can be used to set stronger limits on RPV couplings Summary Summary 13 / 13

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Tuned Hadronization Parameters Tuned Herwig++ hadronization parameters: ClMaxLight : Involved in specifying mass threshold for fission of clusters of light quarks PSplitLight : Controls mass distribution of clusters (of light quarks) produced in cluster fission PwtDIquark : Controls the probability of creating a diquark pair during cluster decay Backup Slides 15 / 13

Experiments: Number of bins Experiment N bins ALEPH 1 CLEO 5 ZEUS 3 CERN ISR 4+4 ALICE 9 ALEPH, p / ¯ 26 p χ 2 from ALEPH proton data weighted down by factor 1/25 to keep it from dominating the parameter determination Backup Slides 16 / 13

Gravitino Dark Matter Thermal production of Gravitinos during reheating can give the right relic density � 2 � � � 100 GeV � � m ˜ g ( µ ) T R G h 2 ≃ 0 . 21 Ω ˜ 10 10 GeV 1 TeV m ˜ G Bolz, Brandenburg, Buchmuller; arXiv:hep-ph/0012052 The reheating temperature T R is weakly constrained, thus so is m ˜ G Backup Slides 17 / 13

Gravitino RPV decays Tree-level Feynman diagrams for decays through ¯ U i ¯ D j ¯ D k -operators Circle indicates RPV coupling Backup Slides 18 / 13

Coupling limits: BESS Current upper limits from GAPS 10 0 95% CL exclusion limits L 1 Q 3 ¯ D 3 10 − 1 assuming 0 observed L 1 Q 1 ¯ D 2 events 10 − 2 U 3 ¯ ¯ D 2 ¯ D 3 10 − 3 U 1 ¯ ¯ D 1 ¯ Somewhat weaker than D 2 10 − 4 existing limits on RPV λ max couplings from 10 − 5 PAMELA ¯ p data 10 − 6 10 − 7 10 − 8 10 − 9 10 1 10 2 10 3 G [GeV] m ˜ Backup Slides 19 / 13

Coupling limits: AMS-02 Prospective upper limits from AMS-02 10 0 95% CL exclusion limits L 1 Q 3 ¯ D 3 10 − 1 assuming 0 TOF events L 1 Q 1 ¯ D 2 and 1 RICH event 10 − 2 U 3 ¯ ¯ D 2 ¯ D 3 10 − 3 U 1 ¯ ¯ D 1 ¯ � 1 expected D 2 10 − 4 background event in λ max the RICH detector 10 − 5 L i Q j ¯ 10 − 6 D k : Slightly weaker 10 − 7 than ¯ p limits at low energies, roughly equal 10 − 8 above a few hundred 10 − 9 10 1 10 2 10 3 GeV G [GeV] m ˜ U i ¯ ¯ D j ¯ D k : Factor ∼ 1 . 5 Stronger than ¯ p limits Backup Slides 20 / 13