1. Search for a low-mass Higgs boson (A0) at BABAR
Arafat Gabareen Mokhtar (SLAC)
On behalf of the BABAR Collaboration
Topics
Y(3S)→γA0, A0→τ+τ-
arXiv:
Submitted to PRL
Y(2S,3S)→γA0, A0→μ+μ-
arXiv:
Y(3S)→γA0,A0→invisible
arXiv:
Preliminary

2. Introduction Minimum SM: single Higgs mass ~ 100 GeV/c2
R. Dermisek, et al.,
PRD 76, (R) (2007)
B(Y→γA0)
A0 non-singlet fraction (cosθA)
Minimum SM: single Higgs mass ~ 100 GeV/c2
MSSM: additional Higgs doublets to give mass to new particles
NMSSM:
additional Higgs singlet to solve the hierarchy problem
Linear combination of singlet with a Higgs doublet leads to CP-odd Higgs state, A0, low mass (A0) < 2mb
Search for A0 in Y(nS)→γA0
mA0<2mτ
2mτ<mA0<7.5 GeV/c2
7.5 <mA0<8.8 GeV/c2
8.8 <mA0<9.2 GeV/c2
F. Wilczek, Phys. Rev. Lett. 39, 1304 (1977)

3. Recent Measurement from CLEO at Y(1S)
In a sample of 25M Y(1S) events, search for Y(1S)→γA0, with
A0→μ+μ-, – 3.5 GeV
A0→τ+τ-, – 9.5 GeV
No evidence for A0
Upper limits in the range (1- 48)×10-5 at 90% C.L.
A0→τ+τ-
A0→μ+μ-
W. Love et. al.,
PRL 101, (2008)
CLEO limits on Υ(1S)→γA0
90% UL B(Y(1S)→γA0)B(A0→ℓℓ)
A0 mass (MeV)

4. Analyses of Y(nS)→gA0 Narrow initial state Radiative Y(nS) Decays:
Y(1S) M= 9,469.3 ± 0.3 MeV
Γ = ± 1.25 KeV
Y(2S) M=10,0233 ± 0.3 MeV
Γ = ± 2.63 KeV
Y(3S) M=10,355.2± 0.5 MeV
Γ = ± 1.85 KeV
Radiative Y(nS) Decays:
Y(nS) → A0 g with
A0→μ+μ-
A0→τ+τ-
A0→invisible
(hint for light dark matter)
In Y(nS) rest frame, photon energy measures mass of A0:
Search for monochromatic photon

5. Search for A0→τ+τ- arXiv:0906.2219μμ ee
Search for three decays modes ττ→ee, ττ→eμ, and ττ→μμ (τ→ℓυℓυτ)
Resolution
Efficiency:
Selection criteria optimized in five Eγ regions (background varies with Eγ)
@ Eγ=0.2 GeV
8 MeV
@ Eγ=4.5 GeV
55 MeV
ee:
10-14 %
eμ:
12-20 %
μμ:
22-26 %

6. Inclusive Photon Spectrum at Y(3S)χb
ττ→ee
Eγ (GeV)
ττ→eμ
ττ→μμ
Principal background from ee→γττ
Peaking background expected at ~760 MeV: Y(3S)→γχbJ(2P), χbJ(2P)→γY(1S,2S), Y(1S,2S)→ττ
No evidence for an enhancement at ~921 MeV for Y(3S)→γηb, ηb→ττ
BABAR preliminary

7. Fits to Eγ distributions
0.2 – 2.0 GeV
2.5 – 4.5 GeV
ττ→ee
ττ→eμ
ττ→μμ
Eγ (GeV) S1
Eγ (GeV)
ττ→ee
ττ→eμ
ττ→μμ S5
BABAR preliminary

8. Scan for Narrow Peaks Eγ (GeV) BABAR preliminary
Subtract fitted smooth background of γ spectrum
Scan in steps equivalent to the half the resolution in Eγ (307 scan points in total)
Simultaneous fits (binned ML) to the 3 different ττ-final states
BABAR preliminary
No evidence for a structure beyond the null Higgs hypothesis…

9. Results of Combined Fits
BABAR preliminary
Y(3S)→γχbJ(2P), χbJ(2P)→γY(1S), Y(1S)→τ+τ-
@ 90% C.L.

10. Search for Y(2S,3S)→γA0, A0→μ+μ-
Exclude regions around
J/ψ and ψ(2S)
Y(2S)
Y(3S)
Combined
BABAR preliminary
Search for narrow enhancement:
ML fit in 1955 mass intervals of 2-5 MeV, covering the range
0.212 ≤ m(A0) ≤ 9.3 GeV,
No evidence for A0→μ+μ-

11. Search for Y(2S,3S)→γA0, A0→μ+μ-
arXiv:
Results after scan
Y(2S)
Y(3S)
&
combined
BABAR preliminary
No evidence for A0→μ+μ- structure beyond the null hypothesis
Upper limit at 90% C.L.

12. Search for A0→invisible ()
arXiv:
Select events with single photon Eγ>2.2 GeV and LARGE missing energy
Search for a peak in Eγ spectrum
No evidence for a signal was observed

13. Summary & Conclusions
BABAR searched for a low-mass Higgs boson A0 in asample of 100M Y(2S) and 122M Y(3S)
The search was performed for Y(nS)→γA0 with in the decay modes A0→μ+μ-, A0→τ+τ-, A0→invisible
No evidence for A0 below 10 GeV/c2 was observed in these decay modes and this data sample
Upper % C.L. were obtained
BF(ηb→μ+μ-)<0.9%, BF(ηb→τ+τ-)<8%

14. BACKUP SLIDES

15. Relevant BABAR data
BABAR Run7
~122 Million Y(3S)
~100 MillionY(2S)