ELFT HÍRADÓ

[Ferenc Siklér <sikler.ferenc AT wigner.hu>]

Kedves kollégák,

 Szeretettel meghívunk minden érdeklődőt a Wigner FK Nagyenergiás Fizikai
Osztályának jövő hétfői szemináriumára, június 16-ra, 10:00-ra.

 Részletek itt (valamint alább)
 https://indico.wigner.hu/event/1689/
 helyszín: 2. épület Médiaterem

 Az előadás a zoom-on keresztül is követhető lesz.

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Dezső Horváth (HUN-REN Wigner FK)

Title: Measurement of the mass of the W boson

Abstract:

The mass of the W boson is one of the most important physical constants as it 
determines the strength and finite range of the charged weak interaction (like 
the beta decay). It is introduced by the Brout-Englert-Higgs mechanism of 
spontaneous symmetry breaking in the Standard Model and can be calculated at 
high precision. It was measured before 2013 by the two Tevatron and four LEP 
experiments and those results agreed very well with each other and the 
calculations. Using these measurements the W mass was determined to be 80387 ± 
15 MeV, which was accepted as a world average [1]. However, 12 years after the 
stop of the Tevatron collider, in 2022 the CDF experiment published a new 
result [2] of high precision, which deviated from the previous ones quite 
significantly: 80433.5 ± 9.4 MeV.

This discrepancy excited the LHC experiments. It is very hard to estimate the W 
mass at hadron colliders. Because of an overwhelming hadron production 
background one has to rely on leptonic decays, where the escaping neutrino 
causes missing energy in the detected events. Two LHC collaborations, ATLAS and 
LHCb in 2022-23 checked proton-proton collision data from the beginning of the 
LHC runs when the rate of the simultaneous collisions was not yet that high as 
later, and have found W masses similar to the world average, although with 
higher uncertainties. In my talk I shall describe a new CMS measurement [3] of 
the W mass relying on the muonic decays of W bosons produced in proton-proton 
collisions at 13 TeV. We have obtained a W mass of 80360.2 ± 9.9 MeV, which has 
a very high precision, agrees with the world average, and contradicts the 2022 
CDF result.

[1] S. Navas et al. (Particle Data Group), Phys. Rev. D 110, 030001 (2024)
[2] T. Aaltonen et al. (CDF), Science 376 170-176 (2022)
[3] V. Chekhovsky et al. (CMS), Submitted to Nature, arXiv:2412.13872 [hep-ex] 
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Üdvözlettel,
 Siklér Ferenc