Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism On the Correlation Between the Spin-Independent and Spin-Dependent Direct Detection of Dark Matter Timothy Cohen with Daniel Phalen and Aaron Pierce arXiv:1001.3408 Michigan Center for Theoretical Physics (MCTP) University of Michigan, Ann Arbor PHENO Symposium May 10, 2010 Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 1/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism Outline Introduction 1 Direct Detection Preliminaries 2 Spin Dependent Cross Sections for Mixed Dark Matter 3 Spin Independent versus Spin Dependent 4 Conclusions and Optimism 5 Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 2/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ WMAP has given us a very precise measurement of the relic density of dark matter: Ω DM ℎ 2 = 0 . 1131 ± 0 . 0034 . ∙ Now we just have to figure out what it is. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 3/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ WMAP has given us a very precise measurement of the relic density of dark matter: Ω DM ℎ 2 = 0 . 1131 ± 0 . 0034 . ∙ Now we just have to figure out what it is. ∙ For this work we will assume that dark matter is a weakly interacting massive particle (WIMP). ∙ We would like to explore the near term prospects for the direct detection of WIMP dark matter. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 3/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ The simplest weak interaction is 휒 D 훾 휇 휒 D ) 푍 0 풪 vector = (¯ 휇 ∙ With a weak scale coefficient, this operator implies a direct detection signal that has been excluded for 푚 DM ≳ 50 TeV. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 4/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ The simplest weak interaction is 휒 D 훾 휇 휒 D ) 푍 0 풪 vector = (¯ 휇 ∙ With a weak scale coefficient, this operator implies a direct detection signal that has been excluded for 푚 DM ≳ 50 TeV. ∙ If the dark matter is Majorana, this operator trivially vanishes. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 4/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ The simplest weak interaction is 휒 D 훾 휇 휒 D ) 푍 0 풪 vector = (¯ 휇 ∙ With a weak scale coefficient, this operator implies a direct detection signal that has been excluded for 푚 DM ≳ 50 TeV. ∙ If the dark matter is Majorana, this operator trivially vanishes. ∙ If we still wish to couple to the 푍 0 , this requires mass mixing between an 푆푈 (2) charged state and a singlet. ∙ This in turn must be proportional to electroweak symmetry breaking. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 4/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ The simplest weak interaction is 휒 D 훾 휇 휒 D ) 푍 0 풪 vector = (¯ 휇 ∙ With a weak scale coefficient, this operator implies a direct detection signal that has been excluded for 푚 DM ≳ 50 TeV. ∙ If the dark matter is Majorana, this operator trivially vanishes. ∙ If we still wish to couple to the 푍 0 , this requires mass mixing between an 푆푈 (2) charged state and a singlet. ∙ This in turn must be proportional to electroweak symmetry breaking. ∙ Hence, the following operators will naively be non-vanishing: 풪 Higgs = (¯ 휒 휒 ) ℎ 휒 훾 휇 훾 5 휒 ) 푍 0 풪 푍 0 = (¯ 휇 ∙ 풪 Higgs and 풪 푍 0 lead to spin-independent and spin-dependent scattering off of nuclei respectively. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 4/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ A canonical example of a Majorana dark matter candidate which interacts with the 푍 0 and ℎ is the MSSM neutralino. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 5/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ A canonical example of a Majorana dark matter candidate which interacts with the 푍 0 and ℎ is the MSSM neutralino. ∙ Many neutralino studies focus on the pure Bino. ∙ Then, in order to reproduce the relic density thermally, one also requires a light slepton. ∙ This is in tension is with LEP due to bounds on the slepton masses. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 5/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ A canonical example of a Majorana dark matter candidate which interacts with the 푍 0 and ℎ is the MSSM neutralino. ∙ Many neutralino studies focus on the pure Bino. ∙ Then, in order to reproduce the relic density thermally, one also requires a light slepton. ∙ This is in tension is with LEP due to bounds on the slepton masses. ∙ However, this tension is alleviated if one considers a mixed (well-tempered) neutralino with 푚 DM > 푚 푊 . Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 5/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ A canonical example of a Majorana dark matter candidate which interacts with the 푍 0 and ℎ is the MSSM neutralino. ∙ Many neutralino studies focus on the pure Bino. ∙ Then, in order to reproduce the relic density thermally, one also requires a light slepton. ∙ This is in tension is with LEP due to bounds on the slepton masses. ∙ However, this tension is alleviated if one considers a mixed (well-tempered) neutralino with 푚 DM > 푚 푊 . ∙ We will show that well-tempering can naturally imply spin-independent and spin-dependent signals for the next generation of experiments. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 5/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism Outline Introduction 1 Direct Detection Preliminaries 2 Spin Dependent Cross Sections for Mixed Dark Matter 3 Spin Independent versus Spin Dependent 4 Conclusions and Optimism 5 Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 6/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ The best limits on dark matter with 푚 DM > 푚 푊 are given by > 5 × 10 − 9 pb and ∙ Define “large” cross sections as 휎 large SI > 10 − 4 pb, motivated by the near term projections of 휎 large SD currently running experiments. Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 7/21
Introduction Direct Detection Preliminaries Spin Dependent Cross Sections for Mixed Dark Matter Spin Independent versus Spin Dependent Conclusions and Optimism ∙ The following operator leads to spin-independent scattering: 풪 SI 푞 = 푐 푞 (¯ 휒 휒 ) (¯ 푞 푞 ) , ∙ In the MSSM (with heavy squarks) the coefficients of the spin-independent operator in the decoupling and large tan 훽 limits is: ( 푍 푊 − 푡 푤 푍 퐵 ) 푍 퐻 푢 ∼ 푐 푢 푚 2 ℎ 푚 2 ( ) 푍 퐻 푑 ℎ ∼ 1 − 푡 훽 푐 푑 푐 푢 푚 2 푍 퐻 푢 퐻 Correlation Between SI and SD Direct Detection Timothy Cohen (University of Michigan) 8/21
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