**Project Acronym: BDM**

**Interested people (during LH)**: Hua-Sheng Shao, Benjamin Fuks, Andreas Goudelis, Genevieve Belanger, Biplob Bhattacherjee, Dipan Sengupta, Nishita Desai, José Zurita, Jose Miguel No, Jan Heisig, Priscilla Pani, Andre Lessa, Sezen Sekmen, Juhi Dutta

**Goal** : study if it's possible to tag SM hadrons (b's going to B's which in turn decay to J/psi's etc) in dark matter long-lived particle searches, when the mass splitting between the parent particle and dark matter is relatively small (< 35 GeV or so).

**Tasks**:

1) Generate the SM background (only bb~ ?)

1.a) Through b/b~->J/psi->mu^+mu^-. The price to pay is 2.0*0.0115*0.05961=1.37e-3 (2.0 from b or b~, F(b->J/psi)=1.15% from FF fit, Br(J/psi->mu^+mu^-)=5.961% from PDG).

1.b) Compare efficiency to usual ISR/FSR search (no loss from J/Psi BRs, but larger BG)

1.c) Compare efficiency to R-hadron (HSCP) searches (with a boosted LLP)

2) Decide on a concrete model and delineate the cosmologically interesting parameter space (from conversion-driven freeze-out, freeze-in etc). Candidate model exists, with a sbottom-like parent decaying into a neutralino-like dark matter + a bottom quark.

3) Generate the signal [UFO model is here + FR file in]

https://phystev.cnrs.fr/wiki/_media/2019:groups:bsm:bdm:sbottom_ufo_model_fr.zip

(from Jan: "MG gives me an error on hypercharge violation, should be checked").
(from Benj: "The error is because mass and gague eigenstates are involved, and no hypercharge can be defined. Just ignore it").

4) Investigate how to improve S/B (e.g. Br(B->l v)=10%, a third lepton veto, B is displaced in signal but not in background etc).


  * [[2019:groups:bsm:bdm:DVresults|Results for the ATLAS DV+MET analysis]]

 

**List of possible benchmarks**

The following parameter points in the "sbottom-neutralino"-simplified model considered in 1705.09292 give you the right relic density via CDFO:

^ m_DM[GeV]     ^ m_sbot[GeV]  ^ \lambda  ^ ctau[m] ^
| 500           | 510          | 2.6e-7  | 0.22    |
| 500           | 520          | 2.6e-7  | 0.05    |
| 1000          | 1010         | 4.6e-7  | 0.14    |
| 1000          | 1020         | 4.8e-7  | 0.03    |
| 1000          | 1030         | 9.7e-6  | 0.003   |

  * [[2019:groups:bsm:bdm:cdfo_sbot_scan_1705_09292.txt| Complete list of points can be seen here ]]
  * [[2019:groups:bsm:bdm:Rhadronlimits| Reinterpreted limits from R-hadron searches (CMS) can be seen here ]]


  * [[2019:groups:bsm:bdm:ToDos| Current Tasks ]]


**References**:

ATLAS Results (J/Psi Background):


[[https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2012-02|{{:2019:groups:session2_bsm:bphy-2012-02_fig_04b.png?direct&400}}]]

[[https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2015-04|{{:2019:groups:session2_bsm:bphy-2015-04_fig_01.png?direct&400}}]]