New Physics Beyond the SM @BESIII Minggang Zhao (on behalf of the - - PowerPoint PPT Presentation

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New Physics Beyond the SM @BESIII Minggang Zhao (on behalf of the - - PowerPoint PPT Presentation

Dec 01, 2022 104 likes •466 views

New Physics Beyond the SM @BESIII Minggang Zhao (on behalf of the BESIII Collaboration) School of Physics, Nankai University, Tianjin, China e + e XII International Workshop on Collision from Phi to Psi February 25 - March 1, 2019,

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New Physics Beyond the SM @BESIII

Minggang Zhao (on behalf of the BESIII Collaboration)

School of Physics, Nankai University, Tianjin, China

XII International Workshop on Collision from Phi to Psi February 25 - March 1, 2019, Novosibirsk, Russia

e+e−

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BESIII Experiment

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BESIII Experiment

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BESIII Experiment

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BESIII Experiment

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New Physics Searches at BESIII

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New Physics Searches at BESIII

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01 Dark Sector

  • Numerous astrophysical observations strongly

suggest the existence of Dark Matter(DM) which provides a hint of dark sector (hidden sector).

  • There might exist some “portals” that connect the SM

sector to DM sector

  • R. Essig et al., arXiv: 1311.0029 (2013)

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01 Dark Sector

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01 Dark Sector: dark photons

PRD99, 012013 (2019)

  • First search for dark photon in E.M. Dalitz decays

⋅ J/ψ → ηγ′, γ′ → e+e− ⋅ J/ψ → η′γ′, γ′ → e+e−

  • Check narrow peaking structures in the me+e- distribution

PRD99, 012006 (2019)

ω, ϕ

PRD99, 012006 (2019) PRD99, 012013 (2019)

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01 Dark Sector: dark photons

  • No obvious peaking structures observed
  • Fit to me+e- of data to obtain signal yields ( regions excluded)
  • Combined limits at 90% C.L. on BF and (Bayesian approach)

ϵ ω, ϕ

PRD99, 012006 (2019) PRD99, 012013 (2019) PRD99, 012006 (2019)

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01 Dark Sector: dark photons

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01 Dark Sector: invisible decay

ℬ(ω → νν) = 8.4 × 10−14, ℬ(ϕ → νν) = 5.8 × 10−12

  • However, if singlet scalar,

pseudo-scalar or vector (portals) exists, and mediates the SM-DM interaction, it can allow invisible decays of SM particles to DM particles.

  • The branching fraction of

invisible decay might be enhanced in the presence of light DM particles.

  • In the SM, quarkonium states can decay into neutrino and anti-neutrino

pair via virtual Z0 boson with very low expected BFs

  • B. McElrath, eConf C070805, 19 (2007)

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01 Dark Sector: invisible decay

  • First search for
  • Recoiling mass (against ) is defined as

η

J/ψ → ηω/ϕ, ω/ϕ → invisible

MV

recoil ≡

(ECM − E3π)2 − | p |2

3π

PRD98, 032001 (2018) PRD98, 032001 (2018)

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01 Dark Sector: invisible decay

  • Fit to to obtain signal yields
  • No obvious signals found, upper limits set at 90% C.L.

MV

recoil

Nω

sig = 1.4 ± 3.6

Nϕ

sig = 1.4 ± 3.6

ℬ(ω → invisible) ℬ(ω → π+π−π0) < 8.1 × 10−5

ℬ(ω → invisible) < 7.3 × 10−5

ℬ(ϕ → invisible) ℬ(ϕ → K+K−) < 3.4 × 10−4

ℬ(ϕ → invisible) < 1.7 × 10−4

PRD98, 032001 (2018) PRD98, 032001 (2018)

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02 BNV

/LNV:

  • Many SM extensions and Grand Unified Theories, such as superstring
  • r SUSY, predict proton decays. In this case, baryon number is violated

while the difference ∆(B-L) is conserved.

  • Searches for new physics at collider experiments are complementary to

those at specifically designed non-collider experiments.

  • Since the matter–antimatter asymmetry in the universe is an observable

fact, the negative result from proton decay experiment does not imply BN is conserved.

arXiv: 1803.04789

J/ψ → Λ+

c e− + c . c .

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02 BNV

/LNV:

  • First search for

J/ψ → Λ+

c e− + c . c . , Λ+ c → pK−π+

  • Check distribution

MpK−π+

  • No events found in the signal window
  • Upper limit at 90% C.L. on BF

ℬ(J/ψ → Λ+

c e− + c . c.) < 6.9 × 10−8

arXiv: 1803.04789

  • The first BNV search in quarkonium decay products.
  • More than two orders of magnitude than that of CLEO’s measurement

in the analogous process D0 → ¯

pe+ + c . c .

J/ψ → Λ+

c e− + c . c .

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02 BNV /LNV:

  • Observations of neutrino oscillation shown that the masses of neutrino

should not be zero.

  • Theoretically, the leading model accommodating the neutrino masses is

the “see-saw” mechanism, in which the SM neutrinos can be Majorana particles.

  • The Majorana neutrinos can be searched through the process violating

the lepton-number (LN) conservation by two units (∆L = 2).

D → Kπe+e+

H.R. Dong et al Chin, Phys. C 39 013101 (2015).

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02 BNV /LNV:

D0 → K−π−e+e+ D+ → K0

Sπ−e+e+

D+ → K−π0e+e+

D → Kπe+e+

  • Check mBC, no signals found

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arXiv: 1902.02450

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02 BNV /LNV:

D0 → K−π−e+e+

arXiv: 1902.02450

D+ → K0

Sπ−e+e+

D+ → K−π0e+e+

D → Kπe+e+

  • Check mBC, no signals found
  • UL at 90% C.L. on BFs

ℬ(D0 → K−π−e+e+) < 2.7 × 10−6 ℬ(D+ → K0

Sπ−e+e+) < 3.3 × 10−6

ℬ(D+ → K−π0e+e+) < 8.5 × 10−6

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arXiv: 1902.02450

ℬ(D0 → K−e+νN(e+π−) ℬ(D0 → K0

Se+νN(e+π−)

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02 BNV /LNV:

D0 → K−π−e+e+

arXiv: 1902.02450

D+ → K0

Sπ−e+e+

D+ → K−π0e+e+

D → Kπe+e+

  • Check mBC, no signals found
  • UL at 90% C.L. on BFs

ℬ(D0 → K−π−e+e+) < 2.7 × 10−6 ℬ(D+ → K0

Sπ−e+e+) < 3.3 × 10−6

ℬ(D+ → K−π0e+e+) < 8.5 × 10−6

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arXiv: 1902.02450 The resultant ULs on the mixing matrix element |VeN|2 as a function of mN provide additional/complementary information about the bounds

  • n the |VeN |2 in D meson decays

ℬ(D0 → K−e+νN(e+π−) ℬ(D0 → K0

Se+νN(e+π−)

ℬ(D0 → K−e+νN(e+π−) ℬ(D0 → K0

Se+νN(e+π−)

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03 FCNC

SD contributions

  • In SM, FCNC is strongly suppressed by GIM mechanism and can happen
  • nly through loop diagram, leading to a very small BF theoretically.
  • The suppression in charm decays is much stronger than those in B and K

system due to stronger diagram cancellation than the down-type quarks.

  • Sensitive to New Physics.

LD contributions

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03 FCNC: D → h(h′)e+e−

  • Most of the

previous D0 limits are at the level of 10-5 ~10-4

  • LHCb observed

some four-body decays of D0→hhµ+µ− at 10-7 level

  • BESIII could

make best constraint on all

  • f the above e+e-

modes

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03 FCNC: D → h(h′)e+e−

PRD97, 072015 (2018)

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03 FCNC: D → h(h′)e+e−

  • Double Tag analysis
  • Absolute BFs
  • Event is very clean, bkg very low
  • High tagging efficiency
  • Many sys. uncertainties cancelled

PRD97, 072015 (2018)

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03 FCNC: D → h(h′)e+e−

  • Double Tag analysis
  • Absolute BFs
  • Event is very clean, bkg very low
  • High tagging efficiency
  • Many sys. uncertainties cancelled

PRD97, 072015 (2018)

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03 FCNC: D → h(h′)e+e−

  • Double Tag analysis
  • Absolute BFs
  • Event is very clean, bkg very low
  • High tagging efficiency
  • Many sys. uncertainties cancelled

PRD97, 072015 (2018)

Data Inclusive MC Sideband

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03 FCNC: D → h(h′)e+e−

  • Double Tag analysis
  • Absolute BFs
  • Event is very clean, bkg very low
  • High tagging efficiency
  • Many sys. uncertainties cancelled

PRD97, 072015 (2018)

Data Inclusive MC Sideband

  • Dominated by the LD bremsstrahlung and (virtual)

resonance decay contributions in the lower and upper regions (dot lines) [JHEP, 04, 135 (2014)].

  • Meþe− distribution is divided into three parts and the

BFs are obtained in the individual regions.

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03 FCNC: D → h(h′)e+e−

PRD97, 072015 (2018)

The likelihood distributions for all the signal modes are shown above, the ULs on the signal BFs at the 90% CL are estimated by integrating the likelihood curves in the physical region of BF>0

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The likelihood distributions for all the signal modes are shown above, the ULs on the signal BFs at the 90% CL are estimated by integrating the likelihood curves in the physical region of BF>0

03 FCNC: D → h(h′)e+e−

  • UL for D+ are obtained for

the first time.

  • UL for D0 are greatly

improved.

  • Divide the Mee distribution
  • f K-𝜌+e+e- into 3 regions

to help separate LD effect.

PRD97, 072015 (2018)

Theoretical[JHEP, 04, 135 (2014)] calculation: ℬtot=1.6×10-5 Experimental result: ℬtot=(2.5±1.1)×10-5

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03 FCNC: ψ(3686) → Λ+

c ¯

pe+e− + c . c .

  • First search for

ψ(3686) → Λ+

c ¯

pe+e− + c . c .

  • Check distribution, No events found in the signal window

MpK−π+

  • Upper limit at 90% C.L. on BF

ℬ(ψ(3686) → Λ+

c ¯

pe+e− + c . c.) < 1.7 × 10−6

PRD97, 091102-R (2018)

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Summary

  • Seven latest analyses (dark, BNV/LNV, FCNC) are introduced.
  • Good electron/positron ID@BESIII, thus we have currently the

best constraint on the channels with e+e- pair.

  • Largest threshold charm data@BESIII, thus we have almost

background free results with DT method.

  • We have 10 B J/ψ data@11 Feb. which is nearly ready for

navigation.

  • More results on new physics@BESIII are coming soon.
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Summary

  • Seven latest analyses (dark, BNV/LNV, FCNC) are introduced.
  • Good electron/positron ID@BESIII, thus we have currently the

best constraint on the channels with e+e- pair.

  • Largest threshold charm data@BESIII, thus we have almost

background free results with DT method.

  • We have 10 B J/ψ data@11 Feb. which is nearly ready for

navigation.

  • More results on new physics@BESIII are coming soon.

Thanks for your a-en/on!

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01 Dark Sector: dark photons

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