A search for lepton flavour violating Z0 decays

Akers, R.; Alexander, G.; Allison, J.; Altekamp, N.; Ametewee, K.; Anderson, K. J.; Anderson, S.; Arcelli, S.; Asai, S.; Axen, D.; Azuelos, G.; Ball, A. H.; Barberio, E.; Barlow, R. J.; Bartoldus, R.; Batley, J. R.; Beaudoin, G.; Bethke, S.; Beck, A.; Beck, G. A.; Beeston, C.; Behnke, T.; Bell, K. W.; Bella, G.; Bentvelsen, S.; Berlich, P.; Bechtluft, J.; Biebel, O.; Bloodworth, I. J.; Bock, P.; Bosch, H. M.; Boutemeur, M.; Braibant, S.; Bright-Thomas, P.; Brown, R. M.; Buijs, A.; Burckhart, H.; B�rgin, R.; Burgard, C.; Capiluppi, P.; Carnegie, R. K.; Carter, A. A.; Carter, J. R.; Chang, C. Y.; Charlesworth, C.; Charlton, D. G.; Chu, S. L.; Clarke, P. E. L.; Clayton, J. C.; Clowes, S. G.; Cohen, I.; Conboy, J. E.; Cooke, O. C.; Cuffiani, M.; Dado, S.; Dallapiccola, C.; Dallavalle, G. M.; Darling, C.; Jong, S. J. De; Pozo, L. A. del; Deng, Hui; Dixit, M. S.; Silva, E. do Couto e; Duboscq, J. E.; Duchovni, E.; Duckeck, G.; Duerdoth, I. P.; Dunwoody, U. C.; Edwards, J. E.G.; Estabrooks, P. G.; Evans, H.; Fabbri, F.; Fabbro, B.; Fanti, M.; Fath, P.; Fiedler, F.; Fierro, M.; Fincke-Keeler, M.; Fischer, H. M.; Folman, R.; Fong, D. G.; Foucher, M.; Fukui, H.; F�rtjes, A.; Gagnon, P.; Gaidot, A.; Gary, J. W.; Gascon, J.; Geddes, N. I.; Geich-Gimbel, Ch.; Gensler, S. W.; Gentit, F. X.; Geralis, T.; Giacomelli, G.; Giacomelli, P.; Giacomelli, Roberto; Gibson, V.; Gibson, W. R.; Gillies, J. D.; Goldberg, J.; Gingrich, D. M.; Goodrick, M. J.; Gorn, W.; Grandi, C.; Gross, E.; Hanson, G.; Hansroul, M.; Hapke, M.; Hargrove, C. K.; Hart, P. A.; Hartmann, C.; Hauschild, M.; Hawkes, C. M.; Hawkings, R. J.; Hemingway, R. J.; Herten, G.; Heuer, R. D.; Hill, J. C.; Hillier, S. J.; Hilse, T.; Hobson, P. R.; Hochman, D.; Homer, R. J.; Honma, A. K.; Howard, Robert; Hughes-Jones, R. E.; Hutchcroft, D. E.; Igo‐Kemenes, P.; Imrie, D. C.; Jawahery, A.; Jeffreys, P. W.; Jérémie, H.; Jimack, M.; Joly, A.; Jones, M.; Jones, Roger; Jovanović, P.; Karlen, D.; Kanzaki, J.; Kawagoe, K.; Kawamoto, T.; Keeler, R.; Kellogg, R. G.; Kennedy, B. W.; King, B. J.; King, J.; Kirk, J.; Kluth, S.; Kobayashi, T.; Kobel, M.; Koetke, D. S.; Kokott, T. P.; Komamiya, S.; Kowalewski, R.; Kress, T.; Krieger, P.; Krogh, J. von; Kyberd, P.; Lafferty, G. D.; Lafoux, H.; Lahmann, R.; Lai, W. P.; Lanske, D.; Lauber, J.; Layter, J. G.; Lee, A. M.; Lefebvre, E.; Lellouch, D.; Letts, J.; Levinson, L. J.; Lloyd, S. L.; Loebinger, F. K.; Long, G. D.; Lorazo, B.; Losty, M. J.; Lou, X.; Ludwig, J.; Luig, A.; Malik, A.; Mannelli, M.; Marcellini, S.; Markus, C.; Martin, A. J.; Martin, J. P.; Mäshimo, T.; Matthews, W.; M�ttig, P.; McKenna, J. A.; Mckigney, E. A.; McMahon, T. J.; McNab, A.; Meijers, F.; Menke, S.; Merritt, F. S.; Mes, H.; Michelini, A.; Mikenberg, G.; Miller, D. J.; Mir, R.; Mohr, W.; Montanari, A.; Mori, T.; Morii, M.; M�ller, U.; Nellen, B.; Nijjhar, B.; O’Neale, S. W.; Oakham, F. G.; Odorici, F.; Ogren, H. O.; Oldershaw, N. J.; Oram, C. J.; Oreglia, M. J.; Orito, S.; Palmonari, F.; Pansart, J. P.; Patrick, G. N.; Pearce, M. J.; Phillips, P. D.; Pilcher, J. E.; Pinfold, J. L.; Plane, D. E.; Poffenberger, P.; Poli, B.; Posthaus, A.; Pritchard, T. W.; Przysiezniak, H.; Redmond, M. W.; Rees, D. L.; Rigby, D.; Rison, M. G.; Robins, S. A.; Rodning, N.; Roney, J. M.; Ros, E.; Rossi, Antônio; Rosvick, M.; Routenburg, P.; Rozen, Y.; Runge, K.; Runólfsson, Ö.; Rust, D. R.; Sasaki, M.; Sbarra, C.; Schaile, A. D.; Schaile, O.; Scharf, F.; Scharff-Hansen, P.; Schenk, P.; Schmitt, B.; Schrder, M.; Schultz‐Coulon, H.‐C.; Sch�tz, P.; Schulz, M.; Schwiening, J.; Scott, W. G.; Settles, M.; Shears, T.; Shen, B. C.; Shepherd‐Themistocleous, C. H.; Sherwood, P.; Siroli, G. P.; Skillman, A.; Skuja, A.; Smith, A. M.; Smith, T. J.; Snow, G. A.; Sobie, R.; S�ldner-Rembold, S.; Springer, R. W.; Sproston, M.; Stahl, A.; Starks, M.; Stegmann, C.; Stephens, K.; Steuerer, J.; Stockhausen, B.; Strom, D.; Szymański, P.; Tafirout, R.; Taras, P.; Tarem, S.; Tecchio, M.; Teixeira-Dias, P.; Tesch, N.; Thomson, M. A.; T�rne, E.; Towers, S.; Tscheulin, M.; Tsukamoto, T.; Turcot, A. S.; Turner-Watson, M. F.; Utzat, P.; Kooten, R. Van; Vasseur, G.; Vikas, P.; Vincter, M. G.; W�ckerle, F.; Wagner, A.; Wagner, D. L.; Ward, C. P.; Ward, D. R.; Ward, J. J.; Watkins, P. M.; Watson, A. T.; Watson, N. K.; Weber, P.; Wells, P. S.; Wermes, N.; Wilkens, B.; Wilson, G. W.; Wilson, J. A.; Włodek, T.; Wolf, G.; Wotton, S. A.; Wyatt, T. R.; Yekutieli, G.; Zacek, V.; Zeuner, W. D.; Zorn, G. T.

doi:10.1007/bf01553981

Cited by 95 publications

(43 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…GeV [7]. The Large Hadron Collider (LHC) has already produced many more Z bosons in pp collisions, but with substantially more background.…”

Section: -94mentioning

confidence: 99%

“…For example, the upper limit on μ → 3e yields BðZ → eμÞ < 10 −12 [5] and on μ → eγ yields BðZ → eμÞ < 10 −10 [6]. The experiments at the Large Electron-Positron Collider (LEP) searched directly for the decay Z → eμ [7][8][9][10]. The most stringent upper limit is BðZ → eμÞ < 1.7 × 10 −6 at the 95% confidence level (C.L.)…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Search for the lepton flavor violating decayZ→eμinppcollisions ats
Aad¹,
Abbott²,
Abdallah³
et al. 2014
Phys. Rev. D
Self Cite
113
7
96
0
View full text Add to dashboard Cite

The ATLAS detector at the Large Hadron Collider is used to search for the lepton flavor violating process Z → eμ in pp collisions using 20.3 fb −1 of data collected at ffiffi ffi s p ¼ 8 TeV. An enhancement in the eμ invariant mass spectrum is searched for at the Z-boson mass. The number of Z bosons produced in the data sample is estimated using events of similar topology, Z → ee and μμ, significantly reducing the systematic uncertainty in the measurement. There is no evidence of an enhancement at the Z-boson mass, resulting in an upper limit on the branching fraction, BðZ → eμÞ < 7.5 × 10 −7 at the 95% confidence level. DOI: 10.1103/PhysRevD.90.072010 PACS numbers: 12.60.-i I. INTRODUCTIONLepton flavor conservation in the charged lepton sector is a fundamental assumption of the Standard Model (SM) but there is no associated symmetry. Thus, searches for lepton flavor violation (LFV) processes are good candidates for probing new physics. The observation of neutrino oscillations is a clear indication of LFV in the neutral lepton sector; however, such an oscillation mechanism cannot induce observable LFV in the charged lepton sector. All searches in the charged lepton sector have produced null results so far [1]. Lepton flavor violation in the charged lepton sector may have a different origin than LFV induced by neutrino oscillations and the search for this effect provides constraints on theories beyond the SM (see for example Refs. [2][3][4]).In this paper, a search for the lepton flavor violating decay Z → eμ is presented. There are stringent experimental limits on other charged lepton flavor violating processes, which can be used to derive an upper limit on the branching fraction for Z → eμ with some theoretical assumptions. For example, the upper limit on μ → 3e yields BðZ → eμÞ < 10 −12 [5] and on μ → eγ yields BðZ → eμÞ < 10 −10 [6]. The experiments at the Large Electron-Positron Collider (LEP) searched directly for the decay Z → eμ [7-10]. The most stringent upper limit is BðZ → eμÞ < 1.7 × 10 −6 at the 95% confidence level (C.L.) using a data sample of 5.0 × 10 6 Z bosons produced in e þ e − collisions at ffiffi ffi s p ¼ 88-94GeV [7]. The Large Hadron Collider (LHC) has already produced many more Z bosons in pp collisions, but with substantially more background. In this paper, the 20.3 AE 0.6 fb −1 [11] of data collected at ffiffi ffi s p ¼ 8 TeV by the ATLAS experiment corresponds to 7.8 × 10 8 Z bosons produced. Despite the larger background at the LHC, a more restrictive direct limit on the Z → eμ decay is reported in this paper. II. ATLAS DETECTORThe ATLAS detector [12] consists of an inner detector (ID) surrounded by a solenoid that produces a 2 T magnetic field, electromagnetic and hadronic calorimeters, and a muon spectrometer (MS) immersed in a magnetic field produced by a system of toroids. The ID measures the trajectories of charged particles over the full azimuthal angle and in a pseudorapidity [13] range of jηj < 2.5 using silicon pixel, silicon microstrip, and straw-tube transitionradiation ...

show abstract

“…GeV [7]. The Large Hadron Collider (LHC) has already produced many more Z bosons in pp collisions, but with substantially more background.…”

Section: -94mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Search for the lepton flavor violating decayZ→eμinppcollisions ats
Aad¹,
Abbott²,
Abdallah³
et al. 2014
Phys. Rev. D
Self Cite
113
7
96
0
View full text Add to dashboard Cite

show abstract

“…CMS uses data-driven techniques to estimate the backgrounds, whereas, ATLAS estimated the background by fitting the data excluding the Z region and then extrapolating it in the Z region. With this analysis, CMS places a limit of 7 × 10 −7 and ATLAS places a limit of 7.5 × 10 −7 on the branching ratio of Z → eµ which is one order of magnitude better than the results from LEP [14].…”

Section: Lvf In Z Decaysmentioning

confidence: 74%

Searches for new phenomena in multilepton final states in ATLAS and CMS

Jain¹

2016

Proceedings of the European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2015)

View full text Add to dashboard Cite

Hints of new physics in B-physics sector have lead to considerable interests on the flavor physics and lepton flavor violating observables at the LHC. Searches for lepton flavor violating decays of the Standard Model particles or new heavy particles have been conducted at the ATLAS and CMS experiment. This talk summarizes Run 1 searches for lepton flavor violating phenomena and new physics in multi-lepton/photon final states.

show abstract

“…The current bounds on the Cs which can be extracted from the OPAL and DELPHI bounds on LFV Z decays [20,21] are given in table 1.…”

Section: Jhep09(2012)092mentioning

confidence: 99%

“…Bounds on lepton flavour changing Z decays (a) from OPAL [20] and (b) from DEL-PHI [21]. The third colomn assumes the decay Z → l…”

Section: Jhep09(2012)092mentioning

confidence: 99%

LHC sensitivity to lepton flavour violating Z boson decays

Davidson

Lacroix

Verdier

2012

J. High Energ. Phys.

View full text Add to dashboard Cite

We estimate that the LHC could set bounds BR(Z → µ ± e ∓ ) < 4.1 × 10 −7 and BR(Z → τ ± µ ∓ ) < 3.5 × 10 −6 (at 95% C.L.) with 20 fb −1 of data at 8 TeV. A similar sensitivity can be anticipated for Z → τ ± e ∓ , because we consider leptonic τ decays such that Z → τ ± µ ∓ → e ± µ ∓ + invisible. These limits can be compared to the LEP1 bounds of order 10 −5 → 10 −6 . Such collider searches are sensitive to a flavour-changing effective Z coupling which is energy dependent, so are complementary to bounds obtained from τ → ℓlℓ and µ → eēe.

show abstract

A search for lepton flavour violating Z0 decays

Cited by 95 publications

References 20 publications

Search for the lepton flavor violating decayZ→eμinppcollisions ats
Aad¹,
Abbott²,
Abdallah³
et al. 2014
Phys. Rev. D
Self Cite
113
7
96
0
View full text Add to dashboard Cite

Search for the lepton flavor violating decayZ→eμinppcollisions ats
Aad¹,
Abbott²,
Abdallah³
et al. 2014
Phys. Rev. D
Self Cite
113
7
96
0
View full text Add to dashboard Cite

Searches for new phenomena in multilepton final states in ATLAS and CMS

LHC sensitivity to lepton flavour violating Z boson decays

Contact Info

Product

Resources

About

A search for lepton flavour violating Z0 decays

Cited by 95 publications

References 20 publications

Search for the lepton flavor violating decayZ→eμinppcollisions atsAad1, Abbott2, Abdallah3 et al. 2014Phys. Rev. DSelf Cite1137960View full textAdd to dashboardCite

Search for the lepton flavor violating decayZ→eμinppcollisions atsAad1, Abbott2, Abdallah3 et al. 2014Phys. Rev. DSelf Cite1137960View full textAdd to dashboardCite

Searches for new phenomena in multilepton final states in ATLAS and CMS

LHC sensitivity to lepton flavour violating Z boson decays

Contact Info

Product

Resources

About

Search for the lepton flavor violating decayZ→eμinppcollisions ats
Aad¹,
Abbott²,
Abdallah³
et al. 2014
Phys. Rev. D
Self Cite
113
7
96
0
View full text Add to dashboard Cite

Search for the lepton flavor violating decayZ→eμinppcollisions ats
Aad¹,
Abbott²,
Abdallah³
et al. 2014
Phys. Rev. D
Self Cite
113
7
96
0
View full text Add to dashboard Cite