Constraints on U(1)L Gauge Boson

Jeong, Yu Seon

Seminar @ Yonsei Univ.2015/09/14

Contents

• Introduction

• Constraints from various experiments- The fifth force search experiments

- Stellar objects

- Low energy laboratory experiments

- Solar neutrino (Borexino)

- Big Bang Nucleosynthesis

- High energy laboratory experiment (LEP)

The Standard Model

The standard model (SM) is very successful in describing the nature of the elementary particles.

It can explain • what are the fundamental particles in

the Universe. • How they interact with each other.

• How the particles have the mass.

But still missing dark matter, neutrino masses and so on.

figure from http://conceptcrucible.com

Our universe composition

The SM can explain only 5%

http://planck.cf.ac.uk/results/cosmic-microwave-background (figure)

First evidence of dark matter

GMm

r2=

mv2

r

http://cdms.phy.queensu.ca/Public_Docs/DM_Intro.html (figure)

Evidences of Dark Matter

Figures from http://cdms.phy.queensu.ca/Public_Docs/DM_Intro.html, and wikipedia

Extension of the SM

If there is an additional U(1) gauge boson, it can mix with the SM photon.

B. Holdom (1986)

Dark Photon - most popular and extensively investigated

- related with the dark matter - could be a solution to (g-2)𝜇

The main references

Extension of the SMAs alternatives, a new gauge boson which can directly couples to the SM particles, e.g. U(1)B-L is investigated.

What we studied is a U(1)L gauge boson, which couples only to the leptons.

=> Difference from dark photon: interaction with neutrinos

• H. S. Lee, Phys. Rev. D90 091702 (2014) - suggested U(1)L model

• R. Harnik, J.Kopp and P. A. N. Machado, JCAP, 1207 026 (2012) - investigated dark photon, U(1)B-L, U(1)B

• J. Heeck - Phys. Lett. B739, 256-263 (2014) - investigated U(1)B-L in a wide mass range

Experimental Constraints

The fifth force search experimentStellar evolution Low energy lab experiment Solar neutrino (Borexino) Big Bang Nucleosynthesis High energy lab experiment (LEP)

V = �GNMAMB

r

⇣1 + ↵e�r/�

⌘Yukawa type correction to the gravitational potential

A. Equivalence Principle Test (𝜆 ≳ 1 cm )

B. Inverse Square Law Test (1 𝜇m ≲ 𝜆 ≲ 1 cm)

C. Casimir Force Test (0.01 𝜇m ≲ 𝜆 ≲ 1𝜇m )

D. Atomic and neutron physics

1. The fifth force search experimentsMZ’ < 10 eV (𝝀 > 0.01 μm)

A. Test of Equivalence Principle

Equivalence Principle :

All objects in a gravitational field have the same acceleration regardless of their mass and the structure.

Torsion balance experiment (e.g. Eot-wash experiment)

figures from S. Schlamminger’s slides

A. Test of Equivalence Principle

Non-zero eta can be interpreted as the effect of the new interaction

T. A. Wanger et. al., Class.Quantum Grav. (2012)

B. Test of Inverse Square Law (1 𝜇m ≲ 𝜆 ≲ 1 cm)

q̃

µ

�=

Z

µ

�for U(1)L

q̃

µ

�=

N

µ

�for U(1)B-L

Vab = ↵Gu2

✓q̃

µ

�

a

q̃

µ

�

b

◆�1 e�r/�

rviolating term of gravitational ISL

V = �GNMAMB

r

⇣1 + ↵e�r/�

⌘

figure from D. J. Kapner et. al. PRL (2007)

C. Test of Casimir force

When the interaction length (𝜆) is smaller than a few 𝜇m, the Casimir force and the electrostatic force exist.

From the measurement to test the Casimir force, the residuals is used to place a limit on the Fnew.

Experimental Constraints

The fifth force search experimentStellar evolutionLow energy lab experiment Solar neutrino (Borexino) Big Bang Nucleosynthesis High energy lab experiment (LEP)

2. Stellar objects

Sun• The new gauge boson (Z’) can be produced inside the Sun by the

plasma excitation. • The escape of the produced Z’ -> the energy loss of the Sun. • Constraint: LZ’ < 0.1 L

Dark Photon Leptonic Gauge Boson

g0L = e�

J.Redondo and G Raffelt, JCAP (2013)

2. Stellar objects

Other stars• Horizontal Branch stars (HB) and Red Giants (RG) provide the

limits in the same way as the Sun. • Temperature is higher than the Sun -> constrain larger Z’ masses. • neutrinos from Z’ decay contribute to the energy loss (RG thru nu).

Dark Photon Leptonic Gauge Boson

g0L = e�

J.Redondo and G Raffelt, JCAP (2013)

2. Stellar objects

Supernova

Leptonic Gauge Boson

• can be considered • In case that neutrinos cannot escape the supernova, the lower

limit exist.

e+e� ! Z 0 ! ⌫⌫̄

Dark Photon

H.K.Dreiner et. al., PRD (2014)

Experimental Constraints

The fifth force search experimentStellar evolutionLow energy lab experimentSolar neutrino (Borexino)Big Bang NucleosynthesisHigh energy lab experiment (LEP)

A. Muon anomalous magnetic moments

2. Low energy lab experiments

There is 3.6𝜎 discrepancy between the measurement and the prediction in SM.

can be the signal of new physics.

1 MeV < MZ’ < 10 GeV

B. Fixed Target Experiment

e.g.) APEX (A’ EXperiment), MAMI (Mainz Microtron)

: search for e+e- signal (e- Z ⟶ e- Z + e+e- )

Dark photon: Br(A’ ⟶ e+e-)≃1 (mA’ < 2m𝜇)

For the dark leptonic gauge boson (Z’), there is the additional decay channel to neutrinos. (Z’ ⟶ e+e-, 𝜈𝜈)

H.Merkel et. al., PRL (2014)

C. BaBar

e+e� ! �A0

A0 ! l+l� (l = e, µ)

e+e� ! � +missing E

Dark Photon

missing E ⟶ DM DM↓

Leptonic Gauge Boson

e+e� ! �Z 0

Z 0 ! l+l� (l = e, µ), ⌫⌫

missing E ⟶ 𝜈𝜈

Br(A0 ! l+l�) ! Br(Z 0 ! l+l�)

a.

b.

Br(A0 ! DM DM) = 1 ! Br(Z 0 ! ⌫⌫)

Constraints from Low Energy Lab

Dark Photon Leptonic Gauge Boson

J.P.Lees et.al.(BaBar), PRL (2014)

Experimental Constraints

The fifth force search experimentStellar evolutionLow energy lab experimentSolar neutrino (Borexino)Big Bang NucleosynthesisHigh energy lab experiment (LEP)

Z’

Cross Sections of Neutrino-electron scattering

Solar neutrino production

pp chain CNO cycle

figures from Borexino collaboration, nature (2014) and P.Mosteiro’s thesis

Solar neutrino spectrum

J.N.Bahcall and A.M.Serenelli, Astrophysical Journal (2005)

Constraints from the solar neutrino (Borexino)

Interaction rate of 862 keV 7Be solar neutrino

�(862 keV 7Be ⌫) = (2.78± 0.13)⇥ 109 cm�2s�1

Pee = 0.51± 0.07 survival probability

R = Ne

Zd�

dE⌫

✓Pee

d�e

dT+ (1� Pee)

d�µ/⌧

dT

◆dE⌫dT

Constraints from the solar neutrino (Borexino)

Experimental Constraints

The fifth force search experimentStellar evolutionLow energy lab experimentSolar neutrino (Borexino)Big Bang NucleosynthesisHigh energy lab experiment (LEP)

4. Big Bang Nucleosynthesis

• During the first several minutes after the Big Bang, the temperature rapidly decreased due to the expansion of the Universe, and the light elements (D, 3He, 4He and 7Li) are produced.

• The predictions of their abundance are in good agreement with the observations. ➜ provide the constraints on the new physics.

• 𝛥N < 1.5

�N = 3

✓g(TBBN )

g(Td)

◆4/3

4. Big Bang Nucleosynthesis

Interaction Rate

J.Heeck (2014)

�(T ) < H(T )

Expansion Rate

Experimental Constraints

The fifth force search experimentStellar evolutionLow energy lab experimentSolar neutrino (Borexino)Big Bang NucleosynthesisHigh energy lab experiment (LEP)

5. LEP (Large Electron Positron Collider)

e+e� ! ff̄

⇤�l+l� = 20.0 TeV

⇤+l+l� = 24.6 TeV

Constraints on a whole parameter space

Preliminary