The “Boggart” of Particle Physics
Dept of Physics Pradipta Ghosh
26th March, 2021 March 26, 2021 1 / 19 “Hogwarts” of the Particle Physics The Standard Model
The Inmates and Laws Elementary Particles Basic Interactions and mediators
Not included in the Standard Model
Image acknowledgement: Harry Potter Wiki, Wikipedia March 26, 2021 2 / 19 Hogwarts of the Particle Physics: The inmates
Elementary Particles and Mediators
DOD: 4 July 2012
The missing piece 1964-2012
1 eV/c2 = 1.783×10−36 kg C = 1 in natural unit system
Neutrinos are Mass-less in the Standard Model
Image acknowledgement: Wikipedia March 26, 2021 3 / 19 Theory: Glashow, 1961, Weinberg, 1967, Salam, 1968
1979 Sheldon Steven Abdus Glashow Weinberg Salam “Hogwarts” of Particle Physics: Founders
Theory: Greenberg, 1964, Han, Nambu, 1964, Bardeen, Fritzsch, Gell-Mann, 1973
C. R. Tom Gerald Theory: Hagen Guralnik 1973 Kibble 2004 David H. D. F. Wilczek Gross Politzer François Theory: Nambu, Peter Englert Jona-Lasinio 1961 Higgs
1999 Robert Gerard Martinus 2013 Brout
2008 't Hooft J. G. Veltman Theory: Brout, Englert, Higgs, Guralnik, Hagen, Kibble, 1964
Yoichiro Nambu Image acknowledgement: Wikipedia March 26, 2021 4 / 19 Muon S. Neddermeyer Electron (1936) (1897) Theory: Pauli, 1930 Tau e-Neutrino (1975) (1956) 1995 Martin Clyde C. D. Anderson Cowan 1995 1906 Lewis Perl t-Neutrino Frederick m -Neutrino (1962) (2000) Carlo Rubbia Reines J. J. Thomson Theory: 1940 DONUT Coll. Theory: 1970
Simon van der Meer 1984 1988 W+,W-,Z UA1, UA2 (1983) CERN Leon M. Melvin Jack The Seekers Theory: Glashow, Weinberg, Salam, 1968 Steinberger Lederman Schwartz Theory: 1973 Gluons Light quarks DORIS (1978) (up,down,strange) PETRA (1979) SLAC (1968) DESY 2008 Theory: Gell-Mann, 1962 T. Maskawa M. Kobayashi 1976 Bottom quark Top quark FermiLAB CDF & D0 Burton Samuel Ting (1977) (1995) 1969 Richter 2013 Murray George Charm quark Higgs boson Gell-Mann Zweig Peter SLAC,BNL (1974) ATLAS, CMS (2012) François Theory: 1964 Higgs Englert Theory: Glashow, LHC-CERN Iliopoulos,Maiani, 1970 Theory: Brout, Englert, Higgs, Guralnik, Hagen, Kibble, 1964 Image acknowledgement: Wikipedia March 26, 2021 5 / 19 Life after Higgs discovery
In reality: I must not tell lies
Unanswered questions:
1. Massive Neutrinos? 2. Why Higgs mass is only 125 GeV? 3. What is dark matter? 4. Why so much matter? 5….. 6….. We NEED to move beyond the Standard Model
Image acknowledgement: Wikipedia March 26, 2021 6 / 19 Massive Neutrinos !!!!!
Neutrinos are Massless within the SM
Neutrinos oscillate in nature: Observed
Arthur Takaaki Theory: Pontecorvo, 1957, 1967, Maki, Nakagawa, Sakata, 1962 McDonald Kajita
Oscillation impossible 2015 WITHOUT Neutrino mass
Not within the SM Image acknowledgement: Wikipedia March 26, 2021 7 / 19 Neutrinos oscillate in nature: Observed
Neutrinos are Massless within the SM
X, Y are nuclei. Detected only 1/3 of the expected event: Solar neutrino problem
Not observed: Atmospheric neutrino problem
Why we are losing certain types?
Image acknowledgement: Wikipedia, Johan Jarnestad March 26, 2021 8 / 19 The “Boggart”: Neutrinos
A Boggart is a shapeshifter (Harry Potter wiki)
For Particle Physics:
Boggart (shape): Neutrinos (Flavours) Poor Wizards: The Physicists
Image acknowledgement: Harry Potter Wiki March 26, 2021 9 / 19 They are everywhere!
Trillions (1012) of neutrinos pass through Your Only 1 interacts on body / second ! average out of 1022 !!! It is indeed a
Image acknowledgement: Wikipedia, Andre de Gouvea March 26, 2021 10 / 19 Why we are losing certain types?
Are they changing their types in motion? How?
Basic idea with a silly example: Consider vectors in 2-dimension
Linear Superposition to construct type “a” and “b” vectors→
Image acknowledgement: Wikipedia, Johan Jarnestad March 26, 2021 11 / 19 Why we are losing certain types?
Another trivial but rather realistic example:
Consider a two-level quantum mechanical system:
Natural Unit System →
Linear Superposition to construct type “a” and “b” wave functions →
After a time span of “t”, we can write →
Image acknowledgement: Wikipedia, Johan Jarnestad March 26, 2021 12 / 19 If we start with “a”, can we get “b” after some time?
Yes: The corresponding quantity is
Vanishes for massless neutrinos
We have used Euler's formula →
We have used Orthonormality conditions →
Remember the vector dot products:
Image acknowledgement: Wikipedia, Johan Jarnestad March 26, 2021 13 / 19 How non-zero is connected with neutrino mass?
Neutrinos have tiny masses:
They are “almost” massless and thus, travel with great speed ~ c
Neglecting mass contribution to the energy:
Which gives →
Lesson 1: Non-zero masses are needed for neutrino oscillations
Lesson 2: Neutrino oscillations can probe squared mass differences, but not the mass scale !!!!!
Image acknowledgement: Wikipedia, Johan Jarnestad March 26, 2021 14 / 19 The reality: Three flavours oscillations
For three flavours:
squared mass differences The “real” picture
Entries of the“U” matrix varies a lot !!!!!
Flavour states Massive states Image acknowledgement: Wikipedia, Johan Jarnestad March 26, 2021 15 / 19 The “U” matrix: in-homogeneous mixing
We can probe squared mass differences What about orderings?
Questions to answer: (food for thought)
1. Why the mixings are so in-homogeneous? 2. How to extend the Standard Model to generate neutrino masses? 3. How to assure tiny neutrino masses? 4. Can we treat neutrinos as dark matter? 5. Can a neutrino act as its anti-particle? . .
. . Image acknowledgement: Wikipedia, Johan Jarnestad March 26, 2021 16 / 19 Models for neutrino masses and mixings
and many many more……..
Which one is the “chosen one”? Time will answer
Image acknowledgement: Wikipedia March 26, 2021 17 / 19 What we Indians are doing….
Bodi West Hills
Image acknowledgement: Wikipedia, Prof. Naba. K. Mondal March 26, 2021 18 / 19
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