Ⅱ-6. Particle Physics

RIKEN Accel. Prog. Rep. 48 (2015)h 0  c c as a test case for quark flavor violation in the MSSM†
A. Bartl,＊1 H. Eberl,＊2 E. Ginina,＊2 K. Hidaka,＊3 ,＊4 and W. Majerotto＊2
It is very important to determine if the SM (StandardModel)-like Higgs boson discovered at the LHC (LargeHadron Collider) in 20121,2) is the SM Higgs boson or theHiggs boson of New Physics. This is the most important
issue in the present particle physics world. In this reportbased on our paper3), we study the possibility that it is thelightest Higgs boson h 0 of the Minimal SupersymmetricStandard Model (MSSM), by focusing on the width of thedecay h 0  c c . We compute the decay width at a fullone-loop level in the DR renormalization scheme in theMSSM with nonminimal Quark Flavor Violation (QFV).
We take our reference QFV scenario as shown in Table 1in Ref.3). The main features of the scenario are: (i) it
contains large c~  ~t (scharm-stop) mixings and large QFVtrilinear couplings of squark-squark Higgs boson, and (ii) itsatisfies the strong constraints on QFV from the B meson
data, where scharm [stop] is the supersymmetry (SUSY)
partner of the charm [top] quark. In this scenario, thelightest up-type squarks u~1 and u~ 2 are strong mixtures of,andthetrilinear
couplings
c~L / R - ~t000( c~L - ~t R - h , c~R - ~tL - h , ~tL - ~t R - h couplings)
are large; therefore, u~1, 2  u~1, 2  h0 couplings are large. Thisleads to an enhancement of the u~1, 2 - u~1, 2 - g~ -loop vertex
correction to the decay amplitude of h 0  c c shown inFig. 1, where g~ is a gluino, which is a hypotheticalsupersymmetric partner of a gluon. Thus, this results in alarge deviation of the MSSM prediction for the decay width- (h0  c c ) from the SM prediction.
In Fig. 2, we show the contour plot of the deviation of theMSSM prediction from the SM prediction  SM (h 0  c c )
uRR
uLR
uLR
uRR
  23 plane, where = 0.118 MeV in the  23and  23.
23~~~~
are the c R - t R and c L - t R mixing parameters,respectively. We see that the MSSM prediction is very
uLR
uRR
sensitive to the QFV parameters  23and  23
, and thatthe deviation of the MSSM prediction from the SM
prediction can be very large (as large as ~ 35%). We havefound that the MSSM prediction becomes nearly equal tothe SM prediction if we switch off all the QFV parametersin our reference QFV scenario.
The observation of any significant deviation of the decay
width from its SM prediction indicates new physics beyondthe SM. It is important to estimate the theoretical andexperimental uncertainties of the width reliably in order toconfirm such a deviation. The relative error of the SM
width is estimated to be ~ 6%4). The relative error of theMSSM width is estimated to be ~ 6%3). As seen in Fig. 2,the deviation of the MSSM width from the SM width can beas large as ~ 35%. Such a large deviation can be observed at a future e e collider ILC (International Linear Collider)with a CM energy 500 GeV and an integrated luminosity of1600 fb-1, where the expected experimental error of thewidth is ~ 3%5). A measurement of the width at LHC is a
hard task because of the difficulties in charm-tagging.
In this report, we have shown that the full one-loop
corrected decay width (h0  c c ) is very sensitive to theQFV parameters in the MSSM. In a scenario with largec~  ~
t mixings, the width can differ up to ~ 35% from its
SM value. After estimating the uncertainties of the width,
we conclude that an observation of these MSSM QFVeffects is possible at ILC. Therefore, we have a good
opportunity to discover the QFV SUSY effect in this decay0h  c c at ILC.

L / R†

Condensed from the article in Phys. Rev. D 91, 015007 (2015)
Institute for Physics, University of Vienna＊2
Institute for High Energy Physics, OEAW, Vienna＊3
Department of Physics, Tokyo Gakugei University＊4
RIKEN Nishina Center＊1

Fig. 1. Gluino-loop vertex correction to h 0  c c .

Fig. 2. Contour plot of the deviation of the full one-loop
0level MSSM width (h  c c ) from the SM widthSM0 (h  c c ) for our reference QFV scenario.
References

1) G. Aad et al.: Phys. Lett. B 716, 1 (2012).
2) S. Chatrchyan et al.: Phys. Lett. B 716, 30 (2012).
3) A. Bartl et al.: Phys. Rev. D 91, 015007 (2015).
4) L. G. Almeida et al.: Phys. Rev. D 89, 033006 (2014).
5) J. Tian and K. Fujii: Proc. EPS-HEP 2013, Stockholm, Sweden,PoS(EPS-HEP2013)316 [arXiv:1311.6528 [hep-ph]].

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