SLIDE 14
Lorenzo Calibbi (Nankai) LFV into ALPs
Past searches: 𝜐 → e a , 𝜐 → 𝜈 a
27 N 50 MeV/c
1400 "''1'' '1'''1'' '1'' 'I'''I'''I'''I''I~A
2~
1000
800 O(m 200 0.2 0.4 06 0,8 I 1.2 1.4 t.6 1.8
Pw [GeWc]
- Fig. 2. Efficiency corrected electron momentum spectrum in the 7- pseudo
rest frame (points with error bars). The solid line represents a fit to the data assuming no contribution from the decay m + ec~ N 50 MeV/c
''1'' '1' ''I'''I'''I'''I'''I'''I''C 1400 1200
80O 600
400
200 ,q 02 0.4 0.6 0.8 1 t .2 1.4 1,6 1.8
Pp~ [GeV/c]
corrected muon momentum spectrum in the r pseudo rest frame (points with elTor bars). The solid line represents a fit to the data assuming no contribution from the decay 7- ---+ /~c~ in order to ensure good momentum resolution and trigger conditions. The following restrictions were made to reduce the two photon and QED backgrounds to a negligible level. We ap- plied a cut on a relation between the transverse momentum balance and the total visible momentum of the charged par- ticles [8]
4 i=1
((e )')
> 4.5 9 p~ 9 c _ 0.55 +0.1 GeV/c
i=1 Ecrns
where pm~ is the transverse momentum of the i-th particle. The shower energy of all charged particles on the three- prong side released in the calorimeter was limited to 3.5
- GeV. On the three-prong side the cosine of the angle be-
tween oppositely charged particles was required to be less than 0.992. To decrease the qq contamination we allowed no more than two photons on the 3-prong side. In a second selection stage we applied cuts specific to the decay channels m -+ euF and m --~ #uF correspondingly. Electrons were required to have momenta greater than 400 MeV/c. In this region the detection efficiency is about 90% and the pion fake rate is 0.5% [4]. The polar angle 0~i~
- f the missing momentum was restricted by the requirement
%- cos(0~is) _> -0.9, where qe is the charge of the detected electron (positron). We have allowed no more than one pho- ton on the one prong side. The photon energy was limited to 300 MeV. The electron sample consisted of 5055 events
[~ 0.06 i, ,,I,,<l~,l,,,i,,,i ,,,i,,,i ,~ ,i, 1
4
1" 004
0.03 0.02 T 0.01 I I I I I I I I P 0.2 0.4 0,6 08 I 1.2 1.4 t.6
c~ Mass [GeV/c 2]
- Fig. 4. The upper limits at 95% confidence
level on the ratio B(T --, s
- -~ guF) for electrons (open squares) and
muons (full squares) with 25 and 17 events resulting from qq contamination and pion misidentification, respectively. For the muon sample the selection procedure depended
- n the lepton momentum. Muon candidates with laboratory
momentum Pl~b > 1.5 GeV/c were required to have hit at least one chamber of the outer layer. In this case the detec- tion efficiency is about 85% and pion fake rate is 2.5%. To suppress the r -+ euF decay contribution the electron like- lihood ratio of the charged track was required to be less than 0.5. In order to suppress background from r --+ pu~ we re- quired that no photons be present on the one-prong side and that the shower energy associated with the charged track be less than 0.5 GeV. The use of the r pseudo rest frame method enables the separation of muons from the background at lab-
- ratory momenta Plab below 1.5 GeV/c, where identification
strategies based on muon penetration through absorber do not work. The backgrounds in this momentum range are mainly due to one-prong r decays into hadrons. A major fraction of two-body hadronic r decays peaks in the high momentum region in the r pseudo rest frame. This com- ponent was rejected by requiring Pv~ < 0.6 GeV/c. The number of events for each part of the muon spectrum is pre- sented in Table 2. The efficiency corrected and background subtracted spectra of electrons and muons in the r pseudo rest frame are shown in Fig. 2 and 3. The background contributions from the r decays and the acceptance for the investigated r decays were estimated from Monte Carlo using the KORALB/TAUOLA generator, the ARGUS detector simulation and subsequent event recon- struction [10-13]. The r decays into a lepton and an unob- servable particle c~ were generated according to the available phase space. The efficiency corrected experimental spectra were fit to a sum of the theoretical expectations for 3- and 2-body r decays for different masses of o~. We have found no excess expected for the r---+ gc~ decays in the whole kinemati- cally allowed region of c~ mass. The upper limits on the ratio of the branching fraction of the decay m --+ gc~ to de- cay r ---+ guF were obtained by a least squares method as a function of c~ mass. In Fig. 4 the results are presented in terms of the ratio of the branching fraction of 2-body decay m ---+ gc~ to the branching fraction of 3-body decay
T --~ ~/J~ .
In summary, a detailed study of the lepton momen- tum spectra for r decays into a lepton and an unobserv-
BR(⌧ → e a) < 2.7 × 10−3 (95% CL) ⇒ Fτe & 4.3 × 106 GeV , BR(⌧ → µ a) < 4.5 × 10−3 (95% CL) ⇒ Fτµ & 3.3 × 106 GeV .
- Z. Phys. C 68, 25-28 (1995)
ZEITSCHRIFT FOR PHYSIK C
9 Springer-Verlag 1995
A search for the lepton-flavour violating decays
T > e(]~ T > ~OL
ARGUS Collaboration
- H. Albrecht, T. Hamacher, R. P. Hofmann, T. Kirchhoff, R. Mankel 1, A. Nan, S. Nowak 1, D. Ref3ing,
- H. Schr6der, H. D. Schulz, M. Walter
~, R. Wurth DESY, Hamburg, Germany
- C. Hast, H. Kapitza, H. Kolanoski, A. Kosche, A. Lange, A. Lindner, M. Schieber, T. Siegmund, B. Spaan, H. Thurn,
- D. T6pfer, D. Wegener
Institut ftir Physik 2, UniversitS.t Dortmund, Germany
- P. Eckstein, C. Frankl, J. Graf, M. Schmidtler, M. Schramm, K. R. Schubert, R. Schwierz, R. Waldi
Institut far Kern- und Teilchenphysik 3, Technische Universit~it Dresden Germany
Physikalisches Institut 4, Universit~it Erlangen-Ntirnberg, Germany
- R. Eckmann, H. Kuipers, O. Mai, R. Mundt, T. Oest, R. Reiner, W. Schmidt-Parzefall
- II. Institut fiir Experimentalphysik,
Universit~it Hamburg, Germany
Institut fur Hochenergiephysik 5, Universit~it Heidelberg, Germany
- K. Ehret, W. Hofmann, A. Htipper, K. T. Kn6pfle, J. Spengler
Max-Planck-Institut fiir Kernphysik, Heidelberg, Germany
6, D. B. MacFarlane 7, J. D. Prentice 6, P. R. B. Saull 7, K. Tzamariudaki 7, R. G. Van de Water 6, T.-S. Yoon 6 Institute of Particle Physics 8, Canada
Institut fiir Experimentelle Kernphysik 9, Universitfit Karlsruhe, Germany
- G. Kernel, P. Kri~an, E. Krignie, T. Podobnik, T. Zivko
Institut J. Stefan and Oddelek za fiziko I~ Univerza v Ljubljani, Ljubljana, Slovenia
- V. Balagura, S. Barsuk, I. Belyaev, R. Chistov, M. Danilov, V. Eiges, L. Gershtein, Yu. Gershtein, A. Golutvin,
- O. Igonkina, I. Korolko, G. Kostina, D. Litvintsev, P. Pakhlov, S. Semenov, A. Snizhko, 1. Tichomirov, Yu. Zaitsev
Institute of Theoretical and Experimental Physics, Moscow, Russia Received: 26 April 1995 1 DESY, IfHM Zeuthen 2 Supported by the German Bundesministerium ffir Forschung und Tech- nologie, under contract number 054DO5 IP 3 Supported by the German Bundesministerium ftir Forscbung und Tech- nologie, under contract number 056DO51P 4 Supported by the German Bundesministerium fiir Forschung und Tech- nologie, under contract number 054ER12P 4 Supported by the German Bundesministerium ftir Forschung und Tech- nologie, under contract number 055HD21P 6 University of Toronto, Toronto, Ontario, Canada 7 McGill University, Montreal, Quebec, Canada s Supported by the Natural Sciences and Engineering Research Council, Canada 9 Supported by the German Bundesministerium ftir Forschung und Tecb nologie, under contract number 055KA11P
- Abstract. Lepton spectra in 7- decays have been studied
with the ARGUS detector at the e+e - storage ring DORIS II at DESY using the "pseudo-rest-frame" technique. We have improved upper limits for two-body ~- -decays into a lepton and an unobservable particle. The problem of fermion families remains one of the central problems in particle physics. The standard SU(3) • SU(2) x U(1) model, as well as its possible "vertical" extensions in the one family framework like SU(5), SU(10) etc., cannot 10 Supported by the Ministry of Science and Technology of the Republic
- f Slovenia and the Internationales Biiro KfA, Jtilich
- Z. Phys. C 68, 25-28 (1995)
ZEITSCHRIFT FOR PHYSIK C
9 Springer-Verlag 1995
A search for the lepton-flavour violating decays
T > e(]~ T > ~OL
ARGUS Collaboration
- H. Albrecht, T. Hamacher, R. P. Hofmann, T. Kirchhoff, R. Mankel 1, A. Nan, S. Nowak 1, D. Ref3ing,
- H. Schr6der, H. D. Schulz, M. Walter
~, R. Wurth DESY, Hamburg, Germany
- C. Hast, H. Kapitza, H. Kolanoski, A. Kosche, A. Lange, A. Lindner, M. Schieber, T. Siegmund, B. Spaan, H. Thurn,
- D. T6pfer, D. Wegener
Institut ftir Physik 2, UniversitS.t Dortmund, Germany
- P. Eckstein, C. Frankl, J. Graf, M. Schmidtler, M. Schramm, K. R. Schubert, R. Schwierz, R. Waldi
Institut far Kern- und Teilchenphysik 3, Technische Universit~it Dresden Germany
Physikalisches Institut 4, Universit~it Erlangen-Ntirnberg, Germany
- R. Eckmann, H. Kuipers, O. Mai, R. Mundt, T. Oest, R. Reiner, W. Schmidt-Parzefall
- II. Institut fiir Experimentalphysik,
Universit~it Hamburg, Germany
Institut fur Hochenergiephysik 5, Universit~it Heidelberg, Germany
- K. Ehret, W. Hofmann, A. Htipper, K. T. Kn6pfle, J. Spengler
Max-Planck-Institut fiir Kernphysik, Heidelberg, Germany
6, D. B. MacFarlane 7, J. D. Prentice 6, P. R. B. Saull 7, K. Tzamariudaki 7, R. G. Van de Water 6, T.-S. Yoon 6 Institute of Particle Physics 8, Canada
Institut fiir Experimentelle Kernphysik 9, Universitfit Karlsruhe, Germany
- G. Kernel, P. Kri~an, E. Krignie, T. Podobnik, T. Zivko
Institut J. Stefan and Oddelek za fiziko I~ Univerza v Ljubljani, Ljubljana, Slovenia
- V. Balagura, S. Barsuk, I. Belyaev, R. Chistov, M. Danilov, V. Eiges, L. Gershtein, Yu. Gershtein, A. Golutvin,
- O. Igonkina, I. Korolko, G. Kostina, D. Litvintsev, P. Pakhlov, S. Semenov, A. Snizhko, 1. Tichomirov, Yu. Zaitsev
Institute of Theoretical and Experimental Physics, Moscow, Russia Received: 26 April 1995 1 DESY, IfHM Zeuthen 2 Supported by the German Bundesministerium ffir Forschung und Tech- nologie, under contract number 054DO5 IP 3 Supported by the German Bundesministerium ftir Forscbung und Tech- nologie, under contract number 056DO51P 4 Supported by the German Bundesministerium fiir Forschung und Tech- nologie, under contract number 054ER12P 4 Supported by the German Bundesministerium ftir Forschung und Tech- nologie, under contract number 055HD21P 6 University of Toronto, Toronto, Ontario, Canada 7 McGill University, Montreal, Quebec, Canada s Supported by the Natural Sciences and Engineering Research Council, Canada 9 Supported by the German Bundesministerium ftir Forschung und Tecb nologie, under contract number 055KA11P
- Abstract. Lepton spectra in 7- decays have been studied
with the ARGUS detector at the e+e - storage ring DORIS II at DESY using the "pseudo-rest-frame" technique. We have improved upper limits for two-body ~- -decays into a lepton and an unobservable particle. The problem of fermion families remains one of the central problems in particle physics. The standard SU(3) • SU(2) x U(1) model, as well as its possible "vertical" extensions in the one family framework like SU(5), SU(10) etc., cannot 10 Supported by the Ministry of Science and Technology of the Republic
- f Slovenia and the Internationales Biiro KfA, Jtilich
ma ≈ 0 : With 472 pb-1:
□ 𝜐 → ea ■ 𝜐 → 𝜈a