MARCH 11YPM 2015  ray from Galactic Center Tanmoy Mondal SRF PRL Dark Matter ?

MARCH 11YPM 2015 DarkMatter You Lunch** ** Figure is for representative purpose. :-(

MARCH 11YPM 2015 In this talk Fermi is not but Also Planck is not

MARCH 11YPM 2015 Study of Galactic cosmic rays and  -ray is very active field Several experiments :  PAMELA  AMS : mounted on International Space Station  Large Area Telescope (LAT): Fermi mounted on Gamma Ray Space Telscope (Fermi) Most detailed map of  -ray sky eve r Complementary experiments :  Microwave : WMAP, Planck  Low Energy: INTEGRAL  Higher energy  - ray : MAGIC,HESS, VERITAS  Neutrinos : IceCube

MARCH 11YPM 2015 Q. What does Fermi-LAT see ? Galactic Emission Extra-Galactic (High Altitude) “isotropic” emission

MARCH 11YPM 2015 Interpretation of Excess Goodenough, Hooper '09 Hooper, Linden '11 Abazajian, Kaplinghat '12 Yusef-Zadeh et al, '12 Hooper, Slatyer '13 Gordon, Macias '13 Huang, Urbano, Xue '13 Linden et al, '13 Abazajian et al, '14 Daylan et al, '14 Millisecond Pulsers (MSP) DM MSP DM Nonthermal bremsstrahlung by e - in molecular clouds DM Nonthermal bremsstrahlung by e - in molecular clouds Interactions between the gas and protons accelerated by Sgr A DM

MARCH 11YPM 2015 Galactic Diffuse Emission All the previous analysis has large systematic uncertainties of background emission : GDE Sources : 1)Boosted   decay  CR scatter inelastically w/ intersteller gas & produce neutral mesons which decays to  pairs. 2)Bremsstrahlung   CR electrons scatter w/ intersteller gas 3)Inverse Compton Scattering  CR electrons up-scatter low-energy photons via ICS into the gamma-ray energy regime trace the gas distribution - different in morphology from DM Can potentially mimic DM signal Depends on : A) CR source distribution and Galactic gas distribution B) Intersteller Radiation Field (ISRF) properties C) Galactic magnetic field magnitude, profile etc... Different assumption on these parameter leads to different GDE models.

MARCH 11YPM 2015 Calore, Cholis, Weniger (CCW) # First study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission. What they have done : ~ ROI : 20 0 X 20 0 square. Mask inner 2 0 along Galactic plane. ~ Photon Energy Range : 300 MeV – 500 GeV ~ Studied 60 GDE models to estimate uncertainties due to assumptions. ~ Full ROI has been broken into TEN sections to analyze Fermi-LAT data.

MARCH 11YPM 2015 Calore, Cholis, Weniger (CCW) Conclusion : -- Robust confirmation of a spherically symmetric excess. -- Centered within 0.05% of GC, hence GCE. -- Spectrum peaks at 1-3 GeV and extends to DM interpretation : hadronic states better than leptonic final states. --  bb with m   GeV.  v ~ 1.78x cm 3 s MSP ? Not likely

MARCH 11YPM 2015 CCWM

MARCH 11YPM 2015 Interpretation depends on GDE Daylan+ CCW Fermi Analysis P6V11

MARCH 11YPM 2015 What about Fermi collaboration's analysis ? f Gamma rays in the energy range 1 GeV GeV ROI = 15 o x15 o square, no masking ( biggest difference from CCW) Examine 4 background interstellar emission models A) Baseline models: Pulsar or OB star cosmic ray source distributions B) Tune intensity and spectral index C) Tune to gamma-rays observed outside ROI D) Determine point sources consistently within these models Excess signal depends strongly on the background model! Preliminary

MARCH 11YPM 2015 GCE is confirmed Astrophysical explanations are less likely DM Interpretation : hadronic final stated better A particle physics motivated DM model to explain the excess Till now Next TM and Tanushree Basak, ArXiv:

MARCH 11YPM 2015 U(1) B-L Extended Standard Model

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MARCH 11YPM 2015 Breit-Wigner enhancement

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MARCH 11YPM 2015 Summary Fermi-LAT sees anomalous gamma rays (1-3 GeV energy range) coming from the inner galaxy Spectrum and morphology prefers annihilating DM to explain the excess Signal appears to be much harder than previously thought (confirms by Fermi preliminary analysis) DM annihilating to bb should have mass ~ 50 GeV U(1) B-L model can explain the excess Breit-Wigner enhancement is necessary to boost the annihilation cross-section today near GC.

MARCH 11YPM 2015 Back Up Slides

MARCH 11YPM 2015 MilliSecond Pulsar

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