Post on 23-Feb-2016
description
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?