---

Home

---

---

---

---

---

Seminari

---

---

---

Home  ⪧  Research  ⪧  Particle Physics  ⪧  MEG/MuEDM

MEG/MuEDM

The international collaboration MEG (Italy, Japan, Switzerland, USA, Russia) searches for the decay μ⁺ -> e⁺ γ at the Paul Scherrer Institut (Zurich). This decay, practically forbidden in the Standard Model of particle physics, is foreseen in many extensions of this model at an experimentally accessible level. The observation of μ⁺ -> e⁺ γ would be a clear signal of New Physics while stringents contraints on its Branching Ratio (BR) allow to set limits on the parameters space of new theoretical models or even to exclude some of them.

Since it is a very rare decay (if it exists) it is necessary to have an intense muon beam; at PSI the most intense continuous muon beam in the world is available, up to 10⁸ muons per second. The MEG experiment is placed at the intensity frontier of New Physics searches, complementary to the energy frontier (LHC).

The MEG final result, based on the analysis of the data taken in 2009-2013 is: BR (μ⁺ -> e⁺ γ) < 4.2 x 10^-13 @ 90% C.L. ( EPJC76,8,434, 2016).It is the world best limit on this decay.

The MEG experiment has been upgraded to the MEG II experiment which is in the data-taking phase since 2021. In a special seminar at the Paul Scherrer Institut, the MEG II Collaboration presented on Oct. 20th 2023 its first results about a new search for this process, based on data collected in 2021, which were published in EPJC 84,216 (2024). By combining them with the previous MEG result, an improved upper limit of BR(mu->egamma) < 3.1 x 10^-13 @ 90% C.L. has been obtained, which is the most stringet limit on this process to date.

The experiment is still taking data and a twenty-fold increase in statistics is foreseen by 2026, with the goal to improve the sensitivity to the decay probability by one order of magnitude with respect to MEG.

The MEG Rome group is also involved in the MuEDM experiment, which searches for the electric dipole moment of the muon. The presence of a permanent electric dipole moment in an elementary particle implies Charge-Parity symmetry violation and thus could help explain the matter-antimatter asymmetry observed in our universe. Within the context of the Standard Model, the electric dipole moment of elementary particles is extremely small, of the order of 10^-38 e·cm. However, many Standard Model extensions, such as supersymmetry, predict large electric dipole moments. The muonEDM experiment has been proposed at the Paul Scherrer Institute in Switzerland to search for the muon electric dipole moment using a 3-T compact solenoid storage ring, and implementing the frozen-spin technique. The experiment, currently in the construction phase, could reach a sensitivity of 6x10^-23e·cm after a year of data taking with the muon beam at the Paul Scherrer Institute, improving the current limit, set by the Muon g-2 experiment at Brookhaven, by more than three orders of magnitudes.

---

Websites:

• MEG/MuEDM Rome
• MEG/MuEDM International
• MuEDM International

Thesis Opportunities:

For information regarding thesis opportunities, please contact: Cecilia Voena and/or visit our local website.

---

Local Coordinator

Cecilia Voena

People    ▽

---