text: 85,87,1469385595814232067,1324170692401639424,Robert McGehee,"I'm very excited about my new paper with @GillyElor and Aaron Pierce: ""Maximizing Direct Detection with HYPER Dark Matter."" So, here's your Fri physics🧵1/n <LINK> <LINK> In this paper, we addressed 2 Qs: #1 What is the maximum cross section for sub-GeV DM scattering off nucleons? #2 Is there a DM candidate which may be detected at future experiments with a cross section as large as this maximum while still accounting for its relic abundance. 2/n The answer to #1: 10^(-36) - 10^(-30) cm^2 for DM masses from 10 keV - 100 MeV. We estimated this by only including present-day bounds on DM and a scalar mediator, which connects the DM to the visible sector. 3/n To establish the model-independence of this max cross section, we considered variations of our starting simple assumptions. No common vector mediators (visibly and invisibly decaying dark photons, B-L, B) had a larger max cross section! 4/n The answer to #2: yes! We named them HighlY interactive ParticlE Relics (HYPERs). 5/n In HYPER models, a dark sector phase transition causes the mediator to decrease its mass to its present-day value. This occurs after the DM abundance freezes-in and boosts the present-day direct detection cross section. 6/n Since DM-SM interactions get a late-time ""boost,"" we must also verify that the DM abundance doesn't change. For parts of HYPER (parameter) space, DM-number-changing processes must be suppressed, causing the direct detection cross section to be smaller than the maximum one. 7/n But, for many HYPERs, we find that they are at (or fairly close to) the maximum consistent cross section! 8/n <LINK> This is particularly exciting because HYPERs populate a parameter space which is imminently testable by many future direct detection efforts but has few DM benchmarks. 9/n In the future, we want to do the same analysis and HYPER model building for sub-GeV DM scattering off electrons which would require an even lower dark sector phase transition temperature. 10/n It is an interesting question as to whether such a low phase transition temperature could modify or remove bounds on the mediator from HB stars, which were essential in our derivation of the maximum cross section for this work. End🧵",https://arxiv.org/abs/2112.03920,"We estimate the maximum direct detection cross section for sub-GeV dark matter scattering off nucleons. For dark matter masses in the range of $10 \text{ keV }- 100 \text{ MeV}$, cross sections greater than $10^{-36}$- $10^{-30} \,\text{cm}^2$ seem implausible. We introduce a dark matter candidate which realizes this maximum cross section: HighlY interactive ParticlE Relics (HYPERs). After HYPERs freeze-in, a dark sector phase transition decreases the mass of the mediator which connects HYPERs to the visible sector. This increases the HYPER's direct detection cross section, but in such a way as to leave the HYPER's abundance unaffected and avoid conflict with measurements of Big Bang Nucleosynthesis and the Cosmic Microwave Background. HYPERs present a benchmark for direct detection experiments in a parameter space with few known dark matter models. ",Maximizing Direct Detection with HYPER Dark Matter,11,"['I\'m very excited about my new paper with @GillyElor and Aaron Pierce: ""Maximizing Direct Detection with HYPER Dark Matter."" So, here\'s your Fri physics🧵1/n\n\n<LINK> <LINK>', 'In this paper, we addressed 2 Qs: #1 What is the maximum cross section for sub-GeV DM scattering off nucleons? #2 Is there a DM candidate which may be detected at future experiments with a cross section as large as this maximum while still accounting for its relic abundance. 2/n', 'The answer to #1: 10^(-36) - 10^(-30) cm^2 for DM masses from 10 keV - 100 MeV. We estimated this by only including present-day bounds on DM and a scalar mediator, which connects the DM to the visible sector. 3/n', 'To establish the model-independence of this max cross section, we considered variations of our starting simple assumptions. No common vector mediators (visibly and invisibly decaying dark photons, B-L, B) had a larger max cross section! 4/n', 'The answer to #2: yes! We named them HighlY interactive ParticlE Relics (HYPERs). 5/n', 'In HYPER models, a dark sector phase transition causes the mediator to decrease its mass to its present-day value. This occurs after the DM abundance freezes-in and boosts the present-day direct detection cross section. 6/n', 'Since DM-SM interactions get a late-time ""boost,"" we must also verify that the DM abundance doesn\'t change. For parts of HYPER (parameter) space, DM-number-changing processes must be suppressed, causing the direct detection cross section to be smaller than the maximum one. 7/n', 'But, for many HYPERs, we find that they are at (or fairly close to) the maximum consistent cross section! 8/n https://t.co/zZCk75LslK', 'This is particularly exciting because HYPERs populate a parameter space which is imminently testable by many future direct detection efforts but has few DM benchmarks. 9/n', 'In the future, we want to do the same analysis and HYPER model building for sub-GeV DM scattering off electrons which would require an even lower dark sector phase transition temperature. 10/n', 'It is an interesting question as to whether such a low phase transition temperature could modify or remove bounds on the mediator from HB stars, which were essential in our derivation of the maximum cross section for this work. End🧵']",21,12,2206