An anomaly-free leptophilic axion-like particle and its flavour violating tests Chengcheng Han ( 韩成成 ) Sun Yat-sen University( 中⼭屲⼤夨学 ) Based on 2007.08834 with Maria López-Ibáñez, Aurora Melis, Oscar Vives, Jin Min Yang Tsung-Dao Lee Institute 2020.9.22
Location of SYSU 韩成成 - 中⼭屲⼤夨学 (SYSU)
Campus of SYSU Wecome to visit! 韩成成 - 中⼭屲⼤夨学 (SYSU)
Electron recoil events in XENON1T(arXiv:2006.09721) Possible explanations by new physics • Solar axions • Neutrino magnetic moment • KeV-scale bosonic DM 1. ALP 2. Dark photon • Boosted dark matter A lot of activities here! One particular question for people here, same excess for PandaX or not? 韩成成 - 中⼭屲⼤夨学 (SYSU)
What is axion-like-particle(ALP)? • Axion-like particles (ALPs) are pseudo Nambu-Goldstone bosons of spontaneously broken global symmetries • If it solves the strong CP problem, usually call it axion • It can be very light due to the existence of the shift symmetry • If it is dark matter candidate, life time need to be long enough and can be produced both by misalignment mechanism or thermal production in the early universe 韩成成 - 中⼭屲⼤夨学 (SYSU)
ALP hinted by Xenon1T F . Takahashi, M. Yamada, W . Yin, 2006.10035 • Coupling with electron e R e L e iq e a − L = m e ¯ f q e = q e R − q e L • No U(1)-U(1)e-U(1)e anomaly Too large coupling with electromagnetic field excluded by X-ray search • No U(1)-SU(3)c-SU(3)c anomaly (can not solve the strong CP problem) Mixing with pion induce too large coupling with electromagnetic field 韩成成 - 中⼭屲⼤夨学 (SYSU)
ALP hinted by Xenon1T • Suppressed coupling with photon m 2 q e α aF µ ν ˜ a F µ ν K. Nakayama, F . Takahashi, T. T. Yanagida, arXiv:1403.7390 m 2 f a 48 π e Few keV f a /q e ∼ 3 × 10 9 GeV An anomaly-free ALP? F . Takahashi, M. Yamada, W . Yin, 2006.10035 韩成成 - 中⼭屲⼤夨学 (SYSU)
Flavor universal global symmetry? Considering the model SM+3N • Tiny neutrino mass via see-saw • Baryon asymmetry from leptogenesis Most simple possibility is U(1)B-L/U(1)L Adding another scalar field Φ (+2) • Spontaneously breaking the global symmetry 1 (majoran) 2( s + f ) e ia/f Φ = √ • Generate the majorana mass for the right-handed neutrino N c N y N ¯ LHN + y Φ ¯ 韩成成 - 中⼭屲⼤夨学 (SYSU)
Flavor universal global symmetry? No tree level coupling with electron! Generated at one loop e N a N e Already flavor violation by loop From see-saw mechanism, m ν ∼ 0 . 1eV m ν ∼ y 2 N v 2 f/C e ∼ 16 π 2 f = 16 π 2 v 2 f N ∼ m ν m N ⇒ y 2 > 10 16 GeV y 2 m ν m N v 2 m N N Too weak interaction with electron! The global symmetry should be Flavor non-universal! 韩成成 - 中⼭屲⼤夨学 (SYSU)
ALP identified as Flaxion/Axiflavon? Y . Ema, K. Hamaguchi, T. Moroi and K. Nakayama, arXiv:1612.05492 L. Calibbi, F . Goertz, D. Redigolo, R. Ziegler and J. Zupan, arXiv:1612.08040 At the same time to explain the fermion mass hierarchy and mixing via Froggatt-Nielsen mechanism The difference here is the flavor symmetry should be anomaly free. 韩成成 - 中⼭屲⼤夨学 (SYSU)
ALP identified as Flaxion/Axiflavon Not easy to cancel U(1)-SU(3)c-SU(3)c anomaly, Only considering the lepton sector: U(1) and a Z2 symmetry H 1 (0) , H 2 ( q H 2 ) , φ (1) L ( q L 1 , q L 2 , q L 3 ) , e ( q e 1 , q e 2 , q e 3 ) , N R (0 , 0 , 0) ij ✏ n e L Y ⊃ Y u ¯ H 1 u + Y d ¯ ij ¯ Q e L i e QH 1 d + c e H 2 e j ij ¯ L i H 2 N j + ( M R ) ij ¯ ij ✏ n ν N R i N c + c ν R j , ✏ = | v φ / Λ | n e ij = q L i − q e j + q H 2 , n ν ij = q L i − q N R,j − q H 2 R | ij ≈ � ij + ✏ n e ij / ✏ n e | U e L | ij = | U e with i ≤ j . jj 韩成成 - 中⼭屲⼤夨学 (SYSU)
ALP identified as Flaxion/Axiflavon Sufficient conditions for anomaly free X X Q L i = 0 , Q e i = 0 i i As a typical example H 1 (0) , H 2 (2) , φ (1) L (1 , 0 , − 1) , e ( − 1 , 0 , 1) , N R (0 , 0 , 0) 1 1 1 4 3 2 n e n ν 2 2 2 ij = 3 2 1 ij = . , 2 1 0 3 3 3 v H 2 ∼ 10 − 2 v EW ✏ = 0 . 1 韩成成 - 中⼭屲⼤夨学 (SYSU)
ALP identified as Flaxion/Axiflavon 1 . 0 1 . 6 1 . 0 With c e ij = 1 . 6 1 . 0 − 2 . 7 ✏ = 0 . 1 . 1 . 0 − 2 . 7 1 . 0 We can reproduce the lepton masses R | ij ≈ � ij + ✏ n e ij / ✏ n e | U e L | ij = | U e with i ≤ j . jj e − µ mixing is O ( ✏ ) ∼ 0 . 1 韩成成 - 中⼭屲⼤夨学 (SYSU)
ALP identified as Flaxion/Axiflavon Scalar potential: 1 H 1 ) 2 + λ 2 ( H † 1 H † 2 H † 2 H 2 + λ 1 ( H † V ( H 1 , H 2 , φ ) = m 2 1 H 1 + m 2 2 H 2 ) 2 2 H 2 ) + λ 4 | H 1 · H 2 | 2 + m 2 H 1 · H 2 + λ ( φ † φ − v 2 + λ 3 ( H † 1 H 1 )( H † φ ) 2 Soft breaking of the U(1) and Z2, giving mass to the ALP • For m around few hundreds GeV to predict mass around keV • Extra Higgses are good targets for LHC and lepton collider • LHC limit is weak because of suppressed coupling with quarks 韩成成 - 中⼭屲⼤夨学 (SYSU)
LFV induced by ALP U e † L M e U e R = Diag( m e , m µ , m τ ) x L = Diag { q L 1 , q L 2 , q L 3 } x R = Diag { q e 1 , q e 2 , q e 3 } Flavor non-universal coupling: − L ae = i ∂ µ a e i γ µ � V e ij + γ 5 A e � e j , ij 2 f a ij = 1 ⇣ ⌘ U e † R + U e † V e R x R U e L x L U e L 2 ij = 1 ⇣ ⌘ U e † R − U e † A e R x R U e L x L U e L 2 Prediction of lepton flavor violation l i → l j a 韩成成 - 中⼭屲⼤夨学 (SYSU)
LFV by ALP � 2 = � 2 + � 2 � C e � � � � V e � � � A e � ij ij ij 韩成成 - 中⼭屲⼤夨学 (SYSU)
Consider a general mixing model Determine the Yukawa structure U (1) ⊂ F Masses and mixings are not fixed by the U(1) charges For example, same charge assignment without all coupling order 1 and v φ / Λ ' O (1) If we take the PMNS matrix totally from charged lepton sector ij = 1 ⇣ ⌘ 2 U e † V e ij , A e U e x R ± x L PMNS . PMNS 韩成成 - 中⼭屲⼤夨学 (SYSU)
Summary and conclusion • The Xenon1T result may indicate an anomaly-free ALP • The origin of such anomaly-free ALP is still mysteries • It may related to the fermion mass structure • Once it is confirmed by future experiment data, it would be very interesting to see whether we can test it by other experiments 韩成成 - 中⼭屲⼤夨学 (SYSU)
back up 韩成成 - 中⼭屲⼤夨学 (SYSU)
If the global symmetry is L(1,0,-1) E(2,0,-2) It can not gauged because U(1)*U(1)*U(1)e anomaly, but it can still give ALP 韩成成 - 中⼭屲⼤夨学 (SYSU)
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