neutrinos at the high energy frontier

Alain Blondel Nuphys2013 2013-12-19

Neutrinos at the High Energy Frontier

Alain Blondel Nuphys2013 2013-12-19

MOTIVATION

The only known BSM physics at the particle physics level is the existence of neutrino masses

-- There is no unique solution for mass terms: Dirac only? Majorana only? Both?

-- if Both, existence of (2 or 3) families of massive right-handed (~sterile) i ,i

neutrinos is predicted («see-saw» models)

masses are unknown (<eV to >1010GeV) -- Arguably, right handed neutrinos are the most likely ‘new physics’ there is

-- can high energy particle physics experiments participate to the search?

Alain Blondel Nuphys2013 2013-12-19 Neutrino physics -- Alain Blondel

Adding masses to the Standard model neutrino 'simply' by adding a Dirac mass term

implies adding a right-handed neutrino (new particle)

No SM symmetry prevents adding then a term like

and this simply means that a neutrino turns into a antineutrino (the charge conjugate of a right handed antineutrino is a left handed neutrino!)

It is perfectly conceivable that both terms are present ‘see-saw’

Alain Blondel TLEP design study r-ECFA 2013-07-20

See-saw in the most general way :

MR 0mD 0Dirac + Majorana mass terms

MR = 0mD 0Dirac only, (like e- vs e+):

L R R L ½ 0 ½ 04 states of equal masses

m

Iweak=

Some have I=1/2 (active)Some have I=0 (sterile)

MR 0mD = 0Majorana only

L R ½ ½ 2 states of equal masses

m

Iweak=

All have I=1/2 (active)

MR 0mD 0Dirac + Majorana

L NR R NL ½ 0 ½ 04 states , 2 mass levels

m

Iweak=

m1 have I=1/2 (~active)m2 have I=0 (~sterile)

Alain Blondel TLEP design study r-ECFA 2013-07-20

Neutrinos : the New Physics there is… and a lot of it! SM Dirac mass term

only Majorana mass term only

Dirac AND Majorana Mass terms

L RI= ½ ½

L R R L ½ 0 ½ 0

L R ½ ½

NR NL 0 0L R ½ ½

X 3 Families X 3 Families X 3 Families X 3 Families

6 massless states 3 masses 12 states3 active neutrinos3 active antinu’s6 sterile neutrinos…3 mixing angles 1 CP violating phase

3 masses 6 active statesNo steriles3 mixing angles 3 CP violating phases0v

6 masses12 states6 active states 6 sterile neutrinos…More mixing angles and CPV phases0v Leptogenesis and Dark matter

Mass hierarchies are all unknown except m1 < m2

Preferred scenario has both Dirac and Majorana terms …… a bonanza of extreme experimental challenges

Alain Blondel Nuphys2013 2013-12-19

Note that this is not necessary as we have no idea of mD and MR !

Alain Blondel Nuphys2013 2013-12-19

= has been invoked to explain the smallness of active neutrino masses

(maybe)

is a pretty large hierarchy problem is’nt it?

... but we dont really know that this implies M MGUT nor that the see-saw mixing is small

nor what is the family dependence of this reasoning.

Alain Blondel Nuphys2013 2013-12-19

-- mixing with active neutrinos leads to various observable consequences -- if very light (eV) , possible effect on neutrino oscillations

-- if mixing in % or permil level, possibly measurable effects on

PMNS matrix unitarity violation and deficit in Z invisible width

occurrence of Higgs invisible decays H ii

violation of unitarity and lepton universality in W or decays -- etc etc..

-- Couplings are small (mD/M) (but who knows?) and generally out of reach of hadron colliders

-- how about high statistics e+e- ?

cos -

Manifestations of right handed neutrinos

c sin

= light mass eigenstateN = heavy mass eigenstate which couples to weak interaction

for one family see-saw (mD/M)

Alain Blondel Nuphys2013 2013-12-19

30 years later and with experience gained on LEP, LEP2 and the B factories we can propose a Z,W,H,t factory of 1000 times the luminosity of LEP2

CERN is launching a 5 years international design study of Circular Colliders 100 TeV pp collider (VHE-LHC) and high luminosity e+e- collider (TLEP) -- kick-off meeting 12-15 February 2014 in Geneva --

Back to the future

Alain Blondel Nuphys2013 2013-12-19

http://arxiv.org/abs/1305.6498.

CONSISTENT SET OF PARAMETERS FOR TLEP TAKING INTO ACCOUNT BEAMSTRAHLUNG

IPAC’13 Shanghai

50 100 150 200 250 300 350 4001E+034

1E+035

1E+036

1E+037

Ecm (GeV)

TLEP Facility Luminosity

Luminosity/cm2/s

Z

WW

ZH

tt

Will consider also : x10 upgrade with e.g. charge compensation? (suppresses beamstrahlung and beam-beam blow up)

Alain Blondel Nuphys2013 2013-12-19 11

• Luminosity : Crossing point between circular and linear colliders ~ 4-500 GeV As pointed out by H. Shopper in ‘The Lord of the Rings’ (Thanks to Superconducting RF…)

Goal performance of e+ e- colliders

Combined know-how {LEP, LEP2 and b-factories} applied for large e+e- ring colliderHigh Luminosity + Energy resolution and Calibration precision on Z, W, H, t

complementarity

Alain Blondel Nuphys2013 2013-12-19

STATISTICS(e+e- ZH, e+e- →W+W-, e+e- → ZH,[e+e-→ t )

TLEP-4 IP, per IP statisticscircumference 80 kmmax beam energy 175 GeVno. of IPs 4 Luminosity/IP at 350 GeV c.m. 1.3x1034 cm-2s-1 106tt pairsLuminosity/IP at 240 GeV c.m. 4.8x1034 cm-2s-1 2 106 ZH evtsLuminosity/IP at 160 GeV c.m. 1.6x1035 cm-2s-1 108 WW pairsLuminosity/IP at 90 GeV c.m. 5.6 1035 cm-2s-1 1012 Z decays

at the Z pole repeat the LEP physics programme in a few minutes…

Alain Blondel Nuphys2013 2013-12-19

to appear in JHEP

Alain Blondel Nuphys2013 2013-12-19

best-of FCC/TLEP #2: Precision EW measts

Asset: -- high luminosity (1012 Z decays + 108 Wpairs + 106 top pairs ) -- exquiste energy calibration up and above WW threshold

Also -- sin2 W 10-6 -- S= 0.0001 from W and Z hadronic widths

-- orders of magnitude on FCNCs and rare decays e.g. Z , e, e in 1011 Z l l events etc. etc.

Design study to establish possibility of theoretical calculations of corresponding precision.

target precisions

Alain Blondel Nuphys2013 2013-12-19

NB without TLEP the SM line would have a 2.2 MeV width

in other words .... ()= 610-6 +several tests of same precision

Alain Blondel Nuphys2013 2013-12-19

In October 1989 LEP determined that the number of neutrino families was 3.110.15

In Feb 1990 Cecilia Jarlskog commented that this number could smaller than 3 if the left handed neutrino(s) has a component of (a) heavy sterile neutrino(s) which is kinematically suppressed or forbidden

Neutrino counting

Alain Blondel Nuphys2013 2013-12-19

Alain Blondel Nuphys2013 2013-12-19

N = 2.984 0.008

Test of the unitarity of the PMNS matrix

This is determined from the Z line shape scan and dominated by the measurement of the hadronic cross-section at the Z peak maximum

The dominant systematic error is the theoreticaluncertainty on the Bhabha cross-section (0.06%)which represents an error of 0.0046 on N

Improving on N by more than a factor 2 would require a large effort to improve on the Bhabha cross-section calculation!

- 2 :^) !!

At the end of LEP:Phys.Rept.427:257-454,2006

Alain Blondel Nuphys2013 2013-12-19

Another solution: determine the number of neutrinos from the radiative returns

e+e- Z ( vv )

in its original form (Karlen) the method only counts the ‘single photon’ eventsand is actually less sensitive than claimed. It has poorer statistics and requires running ~10 GeV above the Z pole. Systematics on photon selection are not small.

present result: Nv= 2.920.05

Alain Blondel Nuphys2013 2013-12-19

given the very high luminosity, the following measurement can be performed

Neutrino counting at TLEP

𝑵 𝒗=

𝜸 𝒁 (𝒊𝒏𝒗)𝜸 𝒁→𝒆𝒆 ,𝝁𝝁𝒆 , (𝑺𝑴 )

The common tag allows cancellation of systematics due to photon selection, luminosityetc. The others are extremely well known due to the availanbility of O(1012 ) Z decays.

The full sensitivity to the number of neutrinos is restored , and the theory uncertainty on is very very small.

A good measurement can be made from the data accumulated at the WW threshold where ( Z(inv) ) ~4 pb for |cos| <0.95

161 GeV (107 s) running at 1.6x1035/cm2/s x 4 exp 3x107 Z(inv) evts, =0.0011adding 5 yrs data at 240 and 350 GeV ............................................................ =0.0008

Optimal (but dedicated ) point at 105 GeV (20pb and higher luminosity) =0.0004?under study.

HF2012 summary Physics-- Alain Blondel 16-11-2012 Fermilab

e+

e-

Z*

Z

H

Z – tagging by missing mass

ILC

total rate gHZZ2

ZZZ final state gHZZ4/ H

measure total width H

empty recoil = invisible width‘funny recoil’ = exotic Higgs decayeasy control below theshold

best-of FCC/TLEP #1: Higgs factory

2 106 ZH events in 5 years

«A tagged Higgs beam».

invisible width = (dark matter?)

4 IPs (2 IPs)

total widthHHHHtt

0.6%28%13%

sensitive to new physics in loops

also (but better done at the hadron colliders HL-LHC, VHE-LHC:

Bes

t acr

oss t

he b

oard

from effect on HZ thresholdarXiv:1312.3322v1 from effect ontt threshold

(constrained fit including ‘exotic’)

24

Higgs Decay into nu + N

Chen, He, Tandean, Tsai (2011)

LEP2 limits (DELPHI)

(projected)

arxiv:1208.3654

Alain Blondel Nuphys2013 2013-12-19

Conclusion and invitation

The study of Future Circular Colliders is starting (CERN, China), including high luminosity e+e- collider.

Precise measurements of the invisible Z and Higgs widths can be made using tagging: e+e- Z and e+e- ZH

There are certainly many more variables that will be sensitive to the existence of heavy right handed neutrinos

What about an ‘invisible’ phenomenology working group for the FCC study?