Previous searches for Heavy Neutral Leptons (and other beam-dump exotics)

A.Rozanov Zurich 10 June 2014

Previous searches for Heavy Neutral Leptons

(and other beam-dump exotics)

Alexandre Rozanov10 June 2014


Standard Coupling Heavy Neutral Lepton

• Stable Dirac m> 45 GeV 95% CL• Stable Majorano m> 39.5 GeV 95% CL• Unstable, Dirac coupling to e,μ,τ m> 90.3 GeV• Unstable, Majorano coupling to e,μ,τ m> 80.5 GeV• In Standard Model with one Higgs doublet sequential chiral Fourth

generation with mN4>55 GeV is excluded by electroweak results with Tevatron and LHC Higgs searches:

gg->triangleQ4->H is enhanced• Small niche with 50 < mN <55 GeV due to H-> N N dominant decay, is

now almost excluded• In SM extension with two Higgs doublets fourth generation is allowed

Vysotsky, Rozanov Phys Lett B700 313 (2011)

Abreu al. Phys Lett B274 230 (1992)

Achard et al. Phys Lett B517 75 (2001)


Search for Heavy Neutrino

• sterile mixed with standard neutrino by matrix U, so small effective couplings

• N produced in pp, decays in empty space equipped with detectors

• PS 191 experiment at CERN 19 GeV PS horn neutrino beam

• CHARM experiment at CERN 400 GeV SPS beam-dump• NuTeV experiment on Fermilab 800 GeV Quad

neutrino beam


Beam dump with PS191 • By product of PS neutrino beam• 19 GeV protons at 128 m distance at 40 mrads• Total exposure of 1.4 1019 protons • He filled decay region of 12 meters


PS191 decay channels• N -> e e ν N -> μ μ ν• N -> μ e ν N -> e π• N -> μ π N -> e π π0

• U2 < 2.0 10-9 at mN=350 MeV


PS191 results• π and K decays

π -> e N K -> μ N K -> e N

Bernardi et al. Phys Lett B203 332 (1988)


Beam Dump with CHARM experiment

• 400 GeV protons at 480 m distance at 10 mrad• Total exposure 2.4 1018 protons• Air decay region of 35 m


CHARM decay channels

• N -> μ μ ν• N -> e e ν• N -> μ e ν• N -> μ X (in WBB)


Electron-neutrino coupling • U2

eN < 1.0 10-7 at mN=1.5 GeV


Muon-neutrino coupling

• U2μN < 0.8 10-7 at mN=1.5 GeV

Dorenbosh et al. Phys Lett B166 473 (1986)


Tau-neutrino coupling• mostly isosinglet heavy neutrino coupled to

tau• re-analysis of CHARM beam dump


Tau-neutrino coupling results• U2

τN < 1.5 10-4 at mN=180 MeVOrloff, Rozanov, Santoni Phys Lett B550 8 (2002)

CHARM

SN1987a

NOMAD

Nucleosynthese


Beam dump with NuTeV • By product of sign selected Quad beam• 800 GeV protons at 1400 m distance at 7.8 mrads• Total exposure of 2.5 1018 protons • He filled decay region of 34 meters


NuTev decay channels

• N -> μ μ ν• N -> μ e ν• N -> μ π• N -> μ ρ


Muon-neutrino coupling• U2

μN < 0.6 10-7 at mN=1.6 GeVVaitaitis et al. Phys Rev Lett 83 4943 (1999)


Exotics: White Quarks in beam dump• Original idea of V. Gribov of screening of color charge via vacuum polarization• M.Strikman point to possible beam-dump search• σ ~ σπ inel (mπ/mglue)2 ~ 10-3 σπ inel

• White Quarks produced in pp collisions can penetrate through muon shielding• CHARM experiment searched WQ in beam dump with 2 1018 protons and

charge measurements by dE/dx in the scintillators

Strikman Phys Lett B105 230 (1981)

Bergsma et al. Z. Phys. C24 217 (1984)


White Quarks in CHARM• CHARM experiment searched WQ in beam dump with 2 1018 protons and charge

measurements by dE/dx in the scintillators• σ < 10-40 cm2 mWQ < 10 GeV

Bergsma et al. Z. Phys. C24 217 (1984)


SHIP vs CHARM

• Total exposure factor = 2.0 1020 /2.4 1018 = 83• Distance = (480m/110m)2=19• Surface = ( 18m2 /9m2)= 2• Decay length = 100m/35m =3• Total = 83*19*2*3= 9462 plus better efficiency• Four order more sensitivity for Heavy Neutrino• Factor 3000 more sensitivity for White Quarks

Previous searches for Heavy Neutral Leptons (and other beam-dump exotics)

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