WIMP ダークマター探査の現状と見通し Shigeki Matsumoto (Kavli IPMU) Collaborators: Members in IPMU WIMP PROJECT S. M., S. Mukhopadhyay, Y. L. Sming Tsai, [JHEP 1410 (2014) 155] S. Banerjee, S. M., K. Mukaida, Y. L. Sming Tsai, [JHEP 16xx (2016) xxx] S. M., S. Mukhopadhyay, Y. L. Sming Tsai, [PRD94 (2016) 065034 ] 以下の WIMP に関する３つの問題に焦点を当て、講演します。 What is the current status of the WIMP scenario? How far can we cover the WIMP scenario in future? What is the leftover remaining as unexplored regions?
1/11 Dark Matter (DM) overview What we know about DM ( ∃ DM established) Neutrality Stability Observations Coldness Abundance DM candidate in the standard model? No DM candidate! (Even a single component pBH is excluded.) DM seems some new particle that is not discovered yet. Mass range of a particle DM Particle dark matter GeV 10 20 10 – 28 de Broglie length < dSph size Compton length > Schwarzschild radius ( l = 2 p /mv) ( l = 2 p /m) (r = 2m/M pl 2 )
2/11 WIMP hypothesis WIMP hypothesis Dark matter is a electromagnetically neutral and stable particle, whose abundance at present is determined by the usual decoupling mechanism. Solving the Boltzmann equation gives Boltzmann eq. tells the following behavior of n WIMP /s → W TH h 2 ～ 0.1 (1pb/< s v>) 2 W OB h 2 ～ 0.12 ± 0.0015 Decoupling (reaction vs. expansion) often plays an important role in U. Mass range WIMP dark matter GeV 10 5 10 – 3 Particle Physicists: The mass of WIMP may have the same origin of the EWSB! Experimenters: WIMP must have some interactions with SM particles, so that there exists a lot of opportunities to detect WIMP! Which SM particle(s) does the WIMP interact with?
3/11 WIMP searches @ Colliders WIMP is expected to be directly produced at colliders, if its energy is high enough. Hadron Collider ： Interaction with quarks. Lepton Collider ： Interaction with leptons. @ Direct detection WIMP can be detected by observing release energy by the scattering off a nucleus. SI scattering ： Int. with quarks & Higgs. SD scattering ： Int. with quarks & Z boson. @ Indirect detection WIMP could be searched for by observing annihilation products produced at DM halo. Gamma ray ： Int. with all the SM particles Cosmic ray ： Int. with all the SM particles
4/11 Studying WIMP without prejudice Discussing WIMP without relying on any specific new physics models! [New physics viewpoint is used to support the region found in the above discussion.] Interac action Which interaction exists =? GeV/c 2 0 DM ? between WIMP and SM? WIMP Classifying WIMPs by each interaction is not useful due to the consistency of FT. ↓ Classifying WIMPs based on its quantum number is more useful for our purpose. Weak charge plays an important role!!! WIMPs can be classified into the following three categories. WIMP has a weak charge of (almost) zero. … Singlet( -like) WIMP WIMP has a weak charge close of (half) integer. … EWIMP WIMP has a mixed weak charge due to EWSB. … Well -tempered WIMP Let us discuss each WIMP using the simplest example to see what kind of strategy is (expected to be) taken to detect it at present (future).
5/11 Well-tempered WIMP The simple lest st exam ample = F Fermion onic c singlet-doubl oublet WIMP model el. Minimal al contents ar are 1 1 0 , 2 2 ½ , 2 –½ due to an anomal aly can ancelat ation. 3 neutral al M Maj ajoran ana a an and 1 1 char arged d Dirac ac fermion on introdu duce ced. d. Lag agran angian an as assuming Z 2 symmetry ry mak aking the WIMP s stab able is is d by [M S , M D , y 1 = ycos q , y 2 = ysin q ] , Par aram ameter spac ace ar are defined nding to [M 1 , m , (g’/ 𝟑 )cos b , (g’/ 𝟑 )sin b ] at corres espo pondi at the MSSM. [DM in interac actions ar are as assumed d to preser erve ve the C CP symmetry.] .] Such a a WIMP is predic icted ed by some nat atural al SUSY scenar arios. s. Scan anning p par aram ameter s r spa pace u e using M g MCMC CMC to clar arify the current stat atus an and fu future p prosp spect cts of th the WI WIMP, as assuming |y |y i i | ≦ 1.
6/11 Well-tempered WIMP @ Near future @ Present After LZ/PICO250 Direct detection is very powerful to explore the well-tempered WIMP! Well-tempered WIMP ← Yukawa interactions → DM-DM-h(Z) couplings The same conclusion is obtained for the most of well-tempered WIMPs, for the origin of the mixing and DM-DM-h(Z) couplings are the same. What we learn: Just waiting future big direct detection experiments!
7/11 EW charged WIMP (EWIMP) The simple lest st exam ample = F Fermion onic c triplet-like ke WIMP MP mod model. l. Minimal al content is 3 0 , , nam amely just o one represen entat ation. 1 neutral al M Maj ajoran ana a an and 1 1 char arged d Dirac ac fermion on introdu duce ced. d. Lag agran angian an as assuming Z 2 symmetry ry mak aking the WIMP s stab able is is Par aram ameter spac ace is simply defined by only o one parameter M T . Such a a WIMP is predat ated ed by the AM AMSB (high-sca cale) scenar arios os. . Scan anning p par aram ameter er sp spac ace is is simp imple le bec becau ause se o of on one par arame meter er. It is possi sible le to in include higher r dimension ional al operat rators rs to ta take new w physic ics s effect cts beyond the WIMP into ac account, howeve wever, r, those do not play important roles at WIMP’s phenomenology.
8/11 EW charged WIMP (EWIMP) LHC @ Near future @ Present Favored Favored The WIMP seems difficult to be detected at DD searches in near future. [ s SI ~ 2 10 – 11 pb, and, in addition, it may be cancelled by BSM contributions. ] LHC will explore the WIMP mass region below 500GeV. Can it go more? IDD searches are promising, for the WIMP’s annihilation is enhanced!!! [The enhancement is from the Sommerfeld effect, Hisano, S.M., Nojiri, 2014.] g -ray obs. (Fermi. CTA) → IDD ( g from dSphs) ← DM dist. (PSC, PFS)
9/11 Singlet-like WIMP The WIMP can annot in interac act wi with SM SM p par articles by al alone d due to th the SM ga gauge s symmetry a y and the Z Z 2 symmet etry, , if it is a a fermion. . Some the other r new w par article （ s ） must be i introdu duce ced d WIMP, wh which is cal alled the m mediat ator or connecting WIMP & SM (p (portal al scenar ario). Phenomen omenol olog ogy of the WIMP depends ds strongly on th the mediat ator. r. When the mediat ator or is h heav avier er enough h than an t the WIMP an and the EW scal ale, the p phenom omenol olog ogy is effectively ly described bed by the E EFT, where L represe wh sents s the e typical al mas ass scal ale of t the mediat ator or. Par aram ameter spac ace is very compl plicat ated, ed, ∃ ar around d 10 p par aram ameters. EWSB, n , & dar The WIMP is p predat ated d in in man any BSMs of E ark sector. r. Scan anning p par aram ameter s r spa pace u e using M g MCMC, CMC, as assuming CP invar arian ance an and th the fl flav avor blindness ss of th the WI WIMP interac action with |c i i | ≦ 1.
10/11 Singlet-like WIMP @ Near future @ Present After LZ/PICO250 Light mediator region Light mediator region Direct detection is powerful to explore the H- & Z-resonance regions. The four Fermi interactions governs the other region with L < 10m DM , [This region is not so much searched for at DD and LHC exps in near future!] LHC results → The four Fermi region ← DD (LZ, PICO250) results ↓ Leptophilic WIMP! [It is governed mainly by the interactions with leptons.]
11/11 Summary We discussed fermionic WIMPs w/o relying on specific BSMs. Well-tempered WIMP: Direct detection searches are (and will be) playing a very important role to explore the WIMP. What we should do is to wait for their results in the near future. Electroweakly charged WIMP (EWIMP): It seems to be the most motivated WIMP from the particle physics viewpoint. Indirect detection searches will be the only way to explore the WIMP in near future, requiring a precision determination of WIMP distribution near by us. Singlet-like WIMP with heavy Mediator: Because of LHC and direct detection searches, leptophilic region will remain unexplored. Experiments sensitive to WIMP-lepton interactions will be very welcome. Singlet-like WIMP with light Mediator: Studies are now on-going by many DM people in the world, via simplified models. Among those, interesting regions are reported, such as the light WIMP in the dark sector, etc.
Recommend
More recommend
