Lepton-Flavor-Violating Decays

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Spring 2009 Summary of 90% C.L. Upper Limits on LFV Tau Decays: (eps) (gif)

Summer 2009 Summary of 90% C.L. Upper Limits on LFV Tau Decays: (eps) (gif)

Lepton Flavor Violating Upper Limit:

♦ τ^- → l^- + γ

Decay Mode	Experiment	Reference	Upper Limit @ 90% C.L.	Luminosity
			(10^-8)	(fb^-1 @ ϒ(4S)) (unless otherwise mentioned)
τ^- → e^- γ	Belle	Phys.Lett.B666:16,2008	12	535
	BaBar	arXiv:0908.2381 [hep-ex]	3.3	470 @ ϒ(4S), 31 @ ϒ(3S), 15 @ ϒ(2S)
τ^- → μ^- γ	Belle	Phys.Lett.B666:16,2008	4.5	535
	BaBar	arXiv:0908.2381 [hep-ex]	4.4	470 @ ϒ(4S), 31 @ ϒ(3S), 15 @ ϒ(2S)

♦ τ^- → l^- + P⁰ (where P⁰ = π⁰, η, η’, K_s)

Decay Mode	Experiment	Reference	Upper Limit @ 90% C.L.	Luminosity
			(10^-8)	(fb^-1 @ ϒ(4S))
τ^- → e^- π⁰	Belle	Phys.Lett.B648:341,2007	8.0	401
	BaBar	Phys.Rev.Lett.98:061803,2008	13	339
τ^- → μ^- π⁰	Belle	Phys.Lett.B648:341,2007	12	401
	BaBar	Phys.Rev.Lett.98:061803,2008	11	339
τ^- → e^- η	Belle	Phys.Lett.B648:341,2007	9.2	401
	BaBar	Phys.Rev.Lett.98:061803,2008	16	339
τ^- → μ^- η	Belle	Phys.Lett.B648:341,2007	6.5	401
	BaBar	Phys.Rev.Lett.98:061803,2008	15	339
τ^- → e^- η’	Belle	Phys.Lett.B648:341,2007	16	401
	BaBar	Phys.Rev.Lett.98:061803,2008	24	339
τ^- → μ^- η’	Belle	Phys.Lett.B648:341,2007	13	401
	BaBar	Phys.Rev.Lett.98:061803,2008	14	339
τ^- → e^- K_s	Belle	EPS2009	2.6	671
	BaBar	Phys.Rev.D79:012004,2009	3.3	469
τ^- → μ^- K_s	Belle	EPS2009	2.3	671
	BaBar	Phys.Rev.D79:012004,2009	4.0	469

♦ τ^- → l^- + S ( where S is a scalar meson)

Decay Mode	Experiment	Reference	Upper Limit @ 90% C.L.	Luminosity
			(10^-8)	(fb^-1 @ ϒ(4S))
τ^- → e^- f₀(980)	Belle	Phys.Lett.B672:317,2009	3.2 (incl. Br(f₀→π⁺π^-))	671
τ^- → μ^- f₀(980)	Belle	Phys.Lett.B672:317,2009	3.4 (incl. Br(f₀→π⁺π^-))	671

♦ τ^- → l^- + V⁰ (where V⁰ is a vector boson)

Decay Mode	Experiment	Reference	Upper Limit @ 90% C.L.	Luminosity
			(10^-8)	(fb^-1 @ ϒ(4S))
τ^- → e^- ρ⁰	Belle	Phys.Lett.B664:35,2008	6.3	543
	BaBar	Phys.Rev.Lett.103:021801,2009	4.6	451
τ^- → μ^- ρ⁰	Belle	Phys.Lett.B664:35,2008	6.8	543
	BaBar	Phys.Rev.Lett.103:021801,2009	2.6	451
τ^- → e^- K^*	Belle	Phys.Lett.B664:35,2008	7.8	543
	BaBar	Phys.Rev.Lett.103:021801,2009	5.9	451
τ^- → μ^- K^*	Belle	Phys.Lett.B664:35,2008	5.9	543
	BaBar	Phys.Rev.Lett.103:021801,2009	17	451
τ^- → e^- K^*	Belle	Phys.Lett.B664:35,2008	7.7	543
	BaBar	Phys.Rev.Lett.103:021801,2009	4.6	451
τ^- → μ^- K^*	Belle	Phys.Lett.B664:35,2008	10	543
	BaBar	Phys.Rev.Lett.103:021801,2009	7.3	451
τ^- → e^- φ	Belle	Phys.Lett.B664:35,2008	7.3	543
	BaBar	Phys.Rev.Lett.103:021801,2009	3.1	451
τ^- → μ^- φ	Belle	Phys.Lett.B664:35,2008	13	543
	BaBar	Phys.Rev.Lett.103:021801,2009	19	451
τ^- → e^- ω	Belle	Phys.Lett.B664:35,2008	18	543
	BaBar	Phys.Rev.Lett.100:071802,2008	11	384
τ^- → μ^- ω	Belle	Phys.Lett.B664:35,2008	8.9	543
	BaBar	Phys.Rev.Lett.100:071802,2008	10	384

♦ τ^- → l^- l⁺ l^-

Decay Mode	Experiment	Reference	Upper Limit @ 90% C.L.	Luminosity
			(10^-8)	(fb^-1 @ ϒ(4S))
τ^- → e^- e⁺ e^-	Belle	EPS2009	2.7	782
	BaBar	CIPANP09	2.9	468
τ^- → μ^- e⁺ e^-	Belle	EPS2009	1.8	782
	BaBar	CIPANP09	2.2	468
τ^- → e^- μ⁺ μ^-	Belle	EPS2009	2.7	782
	BaBar	CIPANP09	3.2	468
τ^- → μ^- μ⁺ μ^-	Belle	EPS2009	2.1	782
	BaBar	CIPANP09	3.3	468
τ^- → e^- μ⁺ e^-	Belle	EPS2009	1.5	782
	BaBar	CIPANP09	1.8	468
τ^- → μ^- e⁺ μ^-	Belle	EPS2009	1.7	782
	BaBar	CIPANP09	2.6	468

♦ τ^- → l^- h⁺ h'^-, l^- h⁰ h⁰, h^- l⁺ h'^-

Decay Mode	Experiment	Reference	Upper Limit @ 90% C.L.	Luminosity
			(10^-8)	(fb^-1 @ ϒ(4S))
τ^- → e^- π⁺ π^-	Belle	arXiv:0908.3156 [hep-ex]	4.4	671
	Babar	Phys.Rev.Lett.95:191801,2005	12	221
τ^- → μ^- π⁺ π^-	Belle	arXiv:0908.3156 [hep-ex]	3.3	671
	Babar	Phys.Rev.Lett.95:191801,2005	29	221
τ^- → e^- π⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	5.8	671
	Babar	Phys.Rev.Lett.95:191801,2005	32	221
τ^- → μ^- π⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	16	671
	Babar	Phys.Rev.Lett.95:191801,2005	26	221
τ^- → e^- K⁺ π^-	Belle	arXiv:0908.3156 [hep-ex]	5.2	671
	Babar	Phys.Rev.Lett.95:191801,2005	17	221
τ^- → μ^- K⁺ π^-	Belle	arXiv:0908.3156 [hep-ex]	10	671
	Babar	Phys.Rev.Lett.95:191801,2005	32	221
τ^- → e^- K⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	5.4	671
	Babar	Phys.Rev.Lett.95:191801,2005	14	221
τ^- → μ^- K⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	6.8	671
	Babar	Phys.Rev.Lett.95:191801,2005	25	221
τ^- → e^- K_s K_s	Belle	EPS2009	7.1	671
τ^- → μ^- K_s K_s	Belle	EPS2009	8.0	671
τ^- → π^- e⁺ π^-	Belle	arXiv:0908.3156 [hep-ex]	8.8	671
	Babar	Phys.Rev.Lett.95:191801,2005	27	221
τ^- → π^- μ⁺ π^-	Belle	arXiv:0908.3156 [hep-ex]	3.7	671
	Babar	Phys.Rev.Lett.95:191801,2005	7.0	221
τ^- → π^- e⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	6.7	671
	Babar	Phys.Rev.Lett.95:191801,2005	18	221
τ^- → π^- μ⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	9.4	671
	Babar	Phys.Rev.Lett.95:191801,2005	22	221
τ^- → K^- e⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	6.0	671
	Babar	Phys.Rev.Lett.95:191801,2005	15	221
τ^- → K^- μ⁺ K^-	Belle	arXiv:0908.3156 [hep-ex]	9.6	671
	Babar	Phys.Rev.Lett.95:191801,2005	48	221

♦ τ^- → Λ + h^- (where h = π, K)

Decay Mode	Experiment	Reference	Upper Limit @ 90% C.L.	Luminosity
			(10^-8)	(fb^-1 @ ϒ(4S))
τ^- → Λ π^-	Belle	Phys.Lett.B632:51,2006	7.2	154
	Babar	Nucl.Phys.Proc.Suppl.169:186-191,2007	5.8	237
τ^- → Λ π^-	Belle	Phys.Lett.B632:51,2006	14	154
	Babar	Nucl.Phys.Proc.Suppl.169:186-191,2007	5.9	237
τ^- → Λ K^-	Babar	Nucl.Phys.Proc.Suppl.169:186-191,2007	15	237
τ^- → Λ K^-	Babar	Nucl.Phys.Proc.Suppl.169:186-191,2007	7.2	237

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