AlakabhaDatta - University of Mississippi Department ... R, d R Quarks ... Murugeswaran Duraisamy...

HET Group: Research Overview

Alakabha Datta

Department of Physics and AstronomyUniversity of Mississippi

September 16, 2014

Alakabha Datta (UM) University of Mississippi September 16, 2014 1 / 17

Particle Physics in the News: Higgs discovery

CMS and Atlas Experiments at the LHC announced the discovery of theHiggs on July 4, 2012. Peter Higgs and Francois Englert win the Nobleprize.

Stephen Hawking says the Higgs will destroy our Universe as we know it!

If you want to understand how the Higgs can destroy the Universe andhow you can save the Universe: Do high energy theory (HET).


The Standard Model

Grand goal of Particle Physics: Understand the basic building blocksof nature and how they interact with themselves.

We have made good progress towards that goal: We have a successfulQuantum theory of the strong, electromagnetic and weak forces.This theory is the Standard Model(SM)

Quantum theory of gravity is missing. But gravity is weak and comesinto play at very high energies the so called Planck scale, MPl .

The discovery of the Higgs confirms the Standard Model (SM) ofParticle Physics. All fundamental particles have been discovered.


Not Happy with the SM

But the fundamental degrees of freedom are too many ( 3 × 16/15).

The Higgs discovery is a problem for the SM. In general, the Higgssector is very unsatisfactory.

There is no dark matter candidate in the SM. The amount of darkmatter we see can be explained by dark matter particle interactingwith SM particles via weak interactions. So dark matter particles(Weakly Interacting Massive Particle, WIMP) should be relevant forthe SM.

We expect a more fundamental theory- we usually call this newphysics- (NP). This theory must be valid at least till quantum gravityeffects become important.

New effects and particles not present in the SM should be discovered.

We are in the business of finding this NP in various channels.


The Standard Model

Almost all physical processes known to us can be understood with theSM.

Fundamental particles of the Standard Model (SM) of particle physics:

SM ≡

(

uLdL

)

uR , dR Quarks(

νLeL

)

eR Leptons spin 12 Matter Particles

uL,R × 3, dL,R × 3, eL,R and νL.

Gauge Bosons ( spin 1): W±, Z 0 g(gluons) γ( photon)-Forces

Higgs ( spin 0) H0: Interacts with the fermions and gauge bosons togive them masses.


The Higgs Mechanism

We are aware of phase change- for example steam to water to ice.

When the universe was very hot at a temperature equivalent to 100 GeV (300 K ≡ 10−2 eV ) there was a phase change when the Higgs, W , Z , thequarks and leptons went from being massless to having masses.

mq.l ∼ y〈0|H|0〉

mW ,Z ∼ g〈0|H|0〉

During the phase transformation the symmetry between the weak and theelectromagnetic interactions was broken making the two forces verydifferent. This is known as electroweak symmetry breaking.


SM problems: Flavor Puzzles

There are threegenerations ofquarks and lep-tons.

MIII > MII > MI

.

Puzzle: Higgs boson interaction should result in similar masses for allparticles- quarks and gauge bosons. (mW ∼ 80 GeV/c2, mZ ∼ 90GeV/c2. Note mp ∼ GeV/c2).

mt ∼ 175 GeV mt ∼ mW ∼ mZ - the only natural quark mass.


Vacuum Instability- Destroying the Universe

At mH = 126 GeV the Higgs potential goes to -∞

V (φ) = −m2

2φ2 +

λ

4!φ4 − (Loop)×mt

mt is large and λ ∼m2

H

(〈0|H|0〉)2is small the quantum correction

dominates and makes V → −∞ or develop a second depperminimum.The Universe can tunnel from the electroweak vacuum to the newvacuum destroying the Universe as we know it.


Vacuum Instability- Saving the Universe

Save the Universe: There is NP and new contribution to the Higgspotential. The Higgs may be made of more fundamental constituents.There may be more than one Higgs.

Higgs vacuum stability in the B-L extended standard model.Alakabha Datta, A. Elsayed, S. Khalil, A. Moursy. Aug 4, 2013. 9 pp.Published in Phys.Rev. D88 (2013) 5, 053011.


What we do: Higgs Physics

If the Higgs is not fundamental it will have different couplings toquarks, leptons, gauge bosons than what is is predicted in theStandard Model.

We are looking at probing the Higgs coupling to light quarks andother rare decays of the Higgs.Probing New Physics in Higgs Couplings to Fermions using anAngular Analysis. Bhubanjyoti Bhattacharya (Montreal U.), AlakabhaDatta (Mississippi U.), David London (Montreal U.). Jul 2, 2014. 15pp. Published in Phys.Lett. B736 (2014) 421-427.

Search for new Higgs bosons: In the decay H → VV we can searchfor signals of new states that the Higgs can decay to: ShanmukaShivashankara.

H → µ+µ− or H → τ+τ− probe the Higgs coupling to leptons.

Higgs effects in low energy as in B decays and neutrino scattering.

Alakabha Datta (UM) University of MississippiSeptember 16, 2014 10 /

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What we do: B Physics

The b quark and top quarks are interesting because they are theheaviest of the quarks and more sensitive to new physics.

Program: In the FCNC are very rare and only arise as quantumcorrections or Loops and are suppressed by small CKM elements E.g.B → φKs ( b → sg).

1 in a million B de-cays: Pure quantumeffect.

Beyond the SM FCNC may occur at tree level or loops and competewith the SM contribution.


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What we do: B Physics: Rare Decays

Study FCNC involving quarks and leptons: E.g. B → µ+µ− (b → sZ ).

1 in a billion B decays:Pure quantum effect.

To study b decays there are so called B factories: BaBar (SLAC,USA), Belle (KEK, Japan), LHCb( CERN) and Belle II ( KEK,Japan).

We are in the list of theorist consulted by these experiments.


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B physics papers

Explaining the B → K ∗µ+µ− data with scalar interactions. AlakabhaDatta, Murugeswaran Duraisamy (Mississippi U.), Diptimoy Ghosh(INFN, Rome). Oct 7, 2013. Published in Phys.Rev. D89 (2014)071501.Searching for new physics with b → sBs0 → V1V2 penguin decays.Bhubanjyoti Bhattacharya (Montreal U.), Alakabha Datta,Murugeswaran Duraisamy (Mississippi U.), David London (MontrealU.). Jun 8, 2013. 12 pp. Published in Phys.Rev. D88 (2013) 1,016007.The Full B → D∗τντ . Angular Distribution and CP violating TripleProducts. Murugeswaran Duraisamy, Alakabha Datta (MississippiU.). Feb 27, 2013. 31 pp. Published in JHEP 1309 (2013) 059.New Physics in b → sµ+µ−: CP-Conserving Observables. AshutoshKumar Alok (Montreal U.), Alakabha Datta (Mississippi U.), AmolDighe (Tata Inst.), Murugeswaran Duraisamy, Diptimoy Ghosh, DavidLondon. Aug 2010. 50 pp. Published in JHEP 1111 (2011) 121.


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What we do: B Physics: Probing Dark matter

The dark matter (DM) is uncharged under the SM interactions. Butit can couple to the Higgs which in turn couples to SM particles.

Many experiments are looking for DM. We know now that DM sectormay have more complicated structure- Flavored DM.

Many signatures of this DM in B physics experiment.


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What we do: Neutrino Physics

Neutrino oscillation means neutrinos have mass and we need newphysics.

This new physics leads to non standard model neutrino interactions(NSI).

The ντ is the last lepton and the second most recent particle of theSM discovered in 2000 at Fermilab. We are studying the ντ NSI.

SHIP collaboration at CERN are using our work to find NSI ντinteractions.


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What we do: Neutrino Physics

Minerva and Super K are looking at ντ neutrinos.

Tau neutrino as a probe of nonstandard interaction. Ahmed Rashed(Mississippi U. & Ain Shams U., Cairo), Preet Sharma, AlakabhaDatta (Mississippi U.). Mar 18, 2013. 21 pp. Published in Nucl.Phys.B877 (2013) 662-682.


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Our Group

PhD: Ahmed Rashed (Completed)Preet SharmaShanmuka Shivashankara

Masters: Hongkai LiuWanwei Wu

Seniors: Alakabha Datta, Muruges Duraisamy

Funding: NSF, USDA.


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