Pis’ma v ZhETF, vol. 109, iss. 6, pp. 367 - 368
© 2019
March 25
Dimuon resonance near 28 GeV and muon anomaly
S. I. Godunov+∗1), V. A. Novikov+×◦1), M. I. Vysotsky+×◦1), E. V. Zhemchugov+×1)
+Institute for Theoretical and Experimental Physics, 117218 Moscow, Russia
∗Novosibirsk State University, 630090 Novosibirsk, Russia
×National Research Nuclear University Moscow Engineering Physics Institute, 115409 Moscow, Russia
◦National Research University Higher School of Economics, 101978 Moscow, Russia
Submitted 4 February 2019
Resubmitted 4 February 2019
Accepted 5
February 2019
DOI: 10.1134/S0370274X19060031
The CMS collaboration has recently reported a peak
An extra scalar or vector can describe the resonance
at invariant mass
discovered in [1], and simultaneously resolve the dis-
agreement between the Standard Model result for the
mX = 28.3 ± 0.4 GeV
(1)
muon anomalous magnetic moment and its measured
value. The total width of the resonance observed in the
of µ+µ- pairs produced in association with b jet in pp-
experiment can be explained by X → ττ and X → νν
collisions at the LHC (Large Hadron Collider) [1]. The
decays. These are the main results of the present paper.
peak appeared in the 8 TeV data with 19.7 fb-1 of inte-
grated luminosity, while no significant excess was found
Though X was found in association with at least
in the 13 TeV data with 35.9 fb-1 of integrated luminos-
one b jet, the simplest model of its production via ra-
ity.2) The observation was made for two event categories
diating from b quark line contradicts the previous CMS
with different cuts on jets directions with the local sig-
paper [4]: while the cuts in the new paper are much
nificancies of 4.2 and 2.9 standard deviations (see the
stronger (mostly cuts on muons) the fiducial cross sec-
paper [1] for the details). The fiducial cross section for
tion is at the level of the upper limit on fiducial cross sec-
both categories is at the level of 4 fb. Signal selection ef-
tion from previous paper. To resolve this contradiction,
ficiency can strongly depend on the production process,
stronger cuts on muons transverse momentum should
so to evaluate the total σ×Br(X → µ+µ-) a particular
not significantly diminish the number of events, i.e., X
model is required. The CMS paper does not study any
should be produced with high transverse momentum.
specific model, so only the fiducial cross sections were
This can be achieved if X is produced in decays of
provided.
a heavy particle, for example, vector-like B quark via
The reported width of the peak is
BLbRX interaction term. The construction of such a
model is the subject of the future work.
Γ(exp)X = 1.8 ± 0.8 GeV
(2)
If the existence of X will be confirmed by future ex-
which is several times larger than the expected mass
perimental data, it will be a strong additional argument
resolution for a dimuon system σµµ = 0.45 GeV.
in favor of muon collider construction.
We study whether the resonance X (if its existence
We are grateful to V. B. Gavrilov, who has
will be confirmed in the future) can explain the devia-
brought the CMS discovery to our attention, and
tion of the measured value of the muon anomalous mag-
to A. N. Nikitenko for valuable comments. We grate-
netic moment aµ ≡ (g -2)µ/2 from the Standard Model
fully acknowledge discussions with R. B. Nevzorov.
value
{
The authors are supported by Russian Founda-
(31.3 ± 7.7) · 10-10, see [2],
δaµ ≡ aexpµ -aSMµ =
(3)
tion for Basic Research under the grant # 16-02-00342.
(26.8 ± 7.6) · 10-10, see [3].
S. I. Godunov is also supported by Russian Foundation
for Basic Research under the grant # 16-32-60115.
1)e-mail: sgodunov@itep.ru; novikov@itep.ru; vysotsky@itep.ru;
zhemchugov@itep.ru
Full text of the paper is published in JETP Letters
2)At 13 TeV the excess can be hidden by the rapid growth of the
background mainly provided by tt events (V. B. Gavrilov, private
journal. DOI: 10.1134/S002136401906002X
communication).
Письма в ЖЭТФ том 109 вып. 5 - 6
2019
367
