Revision of results on 1S 2S and 3S masses

2025-04-29 0 0 96.21KB 4 页 10玖币

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arXiv:2210.13930v1 [hep-ex] 25 Oct 2022

Revision of results on Υ(1S), Υ(2S), and Υ(3S) masses

A.G. Shamova, O.L. Rezanovaa,b

aBudker Institute of Nuclear Physics, 11, akademika Lavrentieva prospect, Novosibirsk, 630090, Russia

bNovosibirsk State University, 1, Pirogova street, Novosibirsk, 630090, Russia

Abstract

We have reconsidered the results on the masses of the narrow bottomonium states Υ(1S)–Υ(3S) obtained in 1982–1986 at CESR,

DORIS and VEPP-4 colliders in order to ﬁx shortcomings of the mass determination procedures. For experiments at CESR and

DORIS this includes the incorrect accounting of the radiative corrections and usage of the electron mass value revised in 1986. In

analyses of all experiments the interference of the resonance production and the nonresonant process was ignored. The corrected

mass values for ﬁve experiments are suggested. The corrections vary from 0.1 to 0.4 MeV. The discrepancy between CESR and

VEPP-4 results on Υ(1S) mass has been reduced from 3.3 to 1.8 standard deviations.

Introduction

The new experiment on the high precision measurement

of the Υ–meson mass has been planned at the VEPP-4M col-

lider [1] with the KEDR detector [2]. The resonant depolariza-

tion method [3, 4] will be used for the beam energy determi-

nation. At the moment the laser polarimeter is under develop-

ment [5] and the test scan of the Υ(1S) has been performed [6].

In this context it is important to overcome known drawbacks

in the analyses of the preceding experiments and correct its re-

sults.

The mass of Υ(1S) was measured by the MD-1 detector at

VEPP-4 [7, 8] and CUSB detector at the collider CESR with

the accuracy of about 0.1 MeV [9]. With lower accuracy of

0.4-0.5 MeV the mass of Υ(2S) was measured by ARGUS and

Crystal Ball detectors at DORIS [10] and by MD-1 [11]. The

mass of Υ(3S) was determined with 0.5 MeV uncertainty by

MD-1 only [11]. In all these experiments the mass values were

obtained by ﬁtting the inclusive hadronic cross section as func-

tion of the c.m. energy. The beam energy was determined using

resonant depolarization method.

In 2000 the results of the mass measurements at VEPP-4

were corrected [12] to the shift of the electron mass value oc-

curred in 1986 [13]. The results from CESR and DORIS stayed

intact.

Another problem to solve is accounting of the radiative cor-

rection in experiments [9] and [10] according to the work [14]

containing the mistake [15]. Despite to the existence of cor-

rect studies of the narrow resonance production since 1975, the

incorrect resonance shape from Ref. [14] was employed for de-

termination of leptonic widths and masses of ψ– and Υ–states

in many experiments. Concerning leptonic widths the problem

was solved in Ref. [16], the corrected values were included in

PDG tables. However, the masses of Υstates [9] and [10] were

not corrected neither in Ref. [16] nor in Ref. [12] where radia-

tive corrections were ﬁxed up for J/ψ mass measurement by the

OLYA detector in 1980 [17]. The MD-1 experiments on masses

of upsilon states [7, 8, 11, 18] were performed with proper ra-

diative correction accounting.

Besides, there is a mistake in the calculation of the reso-

nance curve in Ref. [9], that will be discussed in details below.

The common drawback of all measurements of ψ– and Υ–

state masses mentioned above is ignoring of the interference

between resonant and nonresonant contributions to the hadron

production. First time it was accounted in the J/ψ– and ψ(2S)–

mass measurement in the experiment [19] and was discussed in

details in Ref. [20].

In all experiments under discussion except [9], the depen-

dence of the hadronic cross section on c.m. energy was not pub-

lished. In Refs. [12, 16], in order to correct the resonance lep-

tonic width [16] and mass [12], the equidistant data points were

simulated using the published values of the resonance curve pa-

rameters. Then two ﬁts were performed with the correct ﬁtting

function and that of the published paper. The variation of the

resonance parameter was added to its published value. This

method uses published values of parameters, biased by the in-

correct ﬁt, and does not account for the speciﬁc layout of energy

points.

In contrast with that, in this work we obtained coordinates

of data points from the plots in electronic versions of publi-

cations using the graphical editor and converted them to the

physical quantities. Such data were not absolutely reliable thus

we shifted published values as described above. In Ref. [9] the

measured values of cross section and the energy were published

thus we could just reﬁt the CUSB data.

In the next sections we describe the necessary corrections,

discuss data published by CUSB [9], and then obtain corrected

mass values for three resonances from ﬁve experiments.

1. Change of the electron mass value

As it was mentioned above, the experiments cited did em-

ploy the resonant depolarization method for the beam energy

determination. In this method the measured ratio of the spin

Preprint submitted to Elsevier October 26, 2022

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摘要：

arXiv:2210.13930v1[hep-ex]25Oct2022RevisionofresultsonΥ(1S),Υ(2S),andΥ(3S)massesA.G.Shamova,O.L.Rezanovaa,baBudkerInstituteofNuclearPhysics,11,akademikaLavrentievaprospect,Novosibirsk,630090,RussiabNovosibirskStateUniversity,1,Pirogovastreet,Novosibirsk,630090,RussiaAbstractWehavereconsideredtheresu...

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Revision of results on 1S 2S and 3S masses

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