B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Bogdan Wojtsekhowski, Jefferson Lab
Accelerator based searches for a Dark Force Mediator
1
• Motivation ���
• Existing searches
• Experiments under preparation, APEX
• Plan for the positron storage ring
• Specialized e+e- collider for low s
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Where is new physics
2
In the middle of the 18th century:
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Where is new physics
3
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
SM tests, constraints on new physics (per PDG)
4
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
SM tests, constraints on new physics (per PDG)
5
from STORY05, Y. Semertzidis
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
The motivation is the nature of dark matter
6
1985ApJ...295..422C
Dark Matter: In 1933 by F. Zwicky. This plot from D. Clemens, 1985
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
The motivation is the nature of dark matter
7
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
The DAMA/LIBRA experiment
Bernabei et al. 250 kg radiopure NaI(Tl) the Gran Sasso
NIM A592:297-315,2008
8
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
The DAMA/LIBRA experiment
DAMA collab., arXiv:1308.5109
9
Energy (keV)
S m (c
pd/k
g/ke
V)
-0.05
-0.025
0
0.025
0.05
0 2 4 6 8 10 12 14 16 18 20
2-5 keV
Time (day)
Res
idua
ls (c
pd/k
g/ke
V) DAMA/LIBRA 250 kg (1.04 ton yr)
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
The DAMA/LIBRA experiment
Recoil detection experiment indicates a massive particle.
Where is a mediator of DF?
10
2-5 keV
Time (day)
Res
idua
ls (c
pd/k
g/ke
V) DAMA/LIBRA 250 kg (1.04 ton yr)
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
How to search for new physics
11
W±, Z
Standard Modelquarks, leptons
γg
Hidden Sectordark matter?
A� (massive)X
A�γ
The photon and Aʹ can mix !
mixing induces coupling between ordinary matter and hidden sector matter
�
HoldomGalison, Manohar
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
How to search for new physics
12
X A��
γ
Generated by heavy particles X interacting with andγ A�
X A�γ
� could even be O(1) (theoretically)
∆L =�
2FY,µνF �
µν “Kinetic Mixing”
our photon “heavy photon”
= mixing strength�
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
(“dark photon”)
small coupling
• Large interest in Aʹ search
• Number of considerations
naturally give Aʹ mass ~ 1 - 100s MeV
DM annihilation
Motivation for light dark photon
13
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Positron/electron Antiproton/proton DM annihilation
(“dark photon”)
small coupling
• Large interest in Aʹ search
• Number of considerations
naturally give Aʹ mass ~ 1 - 100s MeV
Motivation for light dark photon
14
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 15
Recent summary of the searches
S. Andreas, C. Niebuhr, A. Ringwald, arXiv:1209.6083
E774
E141Orsay
KEK
E137
Ν-Cal I
CHARMNOMAD& PS191
aΜaeK�ΜΝΓ�KLOE
APEX A1
SM PM
e�e��ΓΜ�Μ�
10�2 10�1 1 10 102
10�7
10�6
10�5
10�4
10�3
10�2
10�1
mΓ' �GeV�
Χε
= g e
A’/g
em
g-2 of muon and electron
Missing particle in e+e- to ..
Decay to SM (e+/e-) - Beam Dump Mass reconstruction
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 16
Recent summary of the searches
S. Andreas, C. Niebuhr, A. Ringwald, arXiv:1209.6083
E774
E141Orsay
KEK
E137
Ν-Cal I
CHARMNOMAD& PS191
aΜaeK�ΜΝΓ�KLOE
APEX A1
SM PM
e�e��ΓΜ�Μ�
10�2 10�1 1 10 102
10�7
10�6
10�5
10�4
10�3
10�2
10�1
mΓ' �GeV�
Χε
= g e
A’/g
em
g-2 of muon and electron
Missing particle in e+e- to γA’
Decay to SM (e+/e-) - Beam Dump Mass reconstruction
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 17
Recent summary of the searches
E774
E141
Orsay
KEKE137
10�2 10�1
10�7
10�6
10�5
10�4
10�3
10�2
mΓ' �GeV�
Χ
S. Andreas, C. Niebuhr, A. Ringwald, arXiv:1209.6083
E774
E141Orsay
KEK
E137
Ν-Cal I
CHARMNOMAD& PS191
aΜaeK�ΜΝΓ�KLOE
APEX A1
SM PM
e�e��ΓΜ�Μ�
10�2 10�1 1 10 102
10�7
10�6
10�5
10�4
10�3
10�2
10�1
mΓ' �GeV�
Χε
= g e
A’/g
em
ε
Lsh Ldec
target
shield
detector
Ltot
E0
e!! "
E!"
e!
e+
No mass reconstruction
Decay inside dump
Statistics limitation
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 18
Recent summary of the searches
S. Andreas, C. Niebuhr, A. Ringwald, arXiv:1209.6083
E774
E141Orsay
KEK
E137
Ν-Cal I
CHARMNOMAD& PS191
aΜaeK�ΜΝΓ�KLOE
APEX A1
SM PM
e�e��ΓΜ�Μ�
10�2 10�1 1 10 102
10�7
10�6
10�5
10�4
10�3
10�2
10�1
mΓ' �GeV�
Χε
= g e
A’/g
em
g-2 of muon and electron
Missing particle in e+e- to ..
Decay to SM (e+/e-) - Beam Dump Mass reconstruction
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 19
Experiments under preparation
slide from R.Essig lecture at PATRAS2012
Detect both e+ and e-: mass reconstruction
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Searches for a gauge boson A’ at JLab
Jefferson Lab site!
C!
A!
B!
D!
FEL!
J.R. Boyce. DARK2012, INFN, Frascati, Italy. 16-19 Oct. 2012. Slide 27 !
20
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Searches for a gauge boson A’ at JLab
James Beacham (NYU) Dark Forces Workshop -- Frascati, Italy -- 16 October 2012
APEX Center for Cosmology and Particle Physics
10
Experimental signature
Direct production at JLab‣ Produce low mass hidden gauge bosons with weak coupling to SM via high energy
electron beam incident on fixed high-Z (Ta) target‣ decays to pair with opening angle ~mA�/Ebe+e−A�
e+
e!
e!
Z
A"
!
Θ0 ≈ 5◦
Dipole septum magnets allow for detection of produced at
small anglese+e−
APEX
21
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Searches for a gauge boson A’ at JLab
APEX
James Beacham (NYU) Dark Forces Workshop -- Frascati, Italy -- 16 October 2012
APEX Center for Cosmology and Particle Physics
20
Final invariant mass spectrum QED radiative trident / Bethe-Heitler events‣ Bump hunt for small, narrow resonance
Bump hunt / resonance search
)2 (MeV/ce+e-m180 190 200 210 220 230 240 250
Even
ts /
( 0.0
5 )
0
200
400
600
800
1000
APEX Test Run Data, ~770K evtsAPEX Test Run Data, ~770K evts
Rescaled Mass0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Even
ts /
( 0.0
0166
389
)
0
100
200
300
400
500
600
700
800
900
=224.525, edm=0.000204, CQ=3A'
TestRunData_6_30_10_27, Wind 30, Cheb O(7), m =224.525, edm=0.000204, CQ=3A'
TestRunData_6_30_10_27, Wind 30, Cheb O(7), m
Window size = 30.5 MeV7th order polynomial fit
P (me+e− | mA� , σ, S, B, ai) =S · N(me+e− | mA� , σ) + B · Polynomial(me+e− , ai)
S + B
λ(S) =L(S, ˆB, ˆai)L(S, B, ai)
Probability model and profile
likelihood ratioTest mass:m = 224.525 MeV
209.525 MeV 240.025 MeV
Test run mass resolution: ~ 0.85 - 1.11 MeVσ
A�
(0.0
5)
APEX Test Run Data: Example Window
224.5 MeV
240.0 MeV 209.5 MeV
22
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Searches for a gauge boson A’
the g-2= ae, aµ,
VEPP-3, and a portion of DarkLight
are sensitive
to “invisible” A’ decay modes
23
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Ways to search for a new particle
Search for a bump in the mass spectra
As it was done - Vector Mesons, Z, H
Required beam: energy, intensity, duty factor���
How small is the e+e- decay branching fraction?
24
e+e− ↔ γ∗ and e+e− ↔ A�
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Options for an e+e- experiment at low s
A “very” low energy, s1/2 ~ 30-100 MeV
a) 15 MeV x 15 MeV e+e- collider =>
b) Sliding beams of e+e- (500 MeV x 500 MeV at 25o)=> Project needs a specialized accelerator with two rings
c) Current approach is a positron beam + atomic electrons
25
L ∼ 1024
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Where to find a positron beam? A beam of 25 nA 400 MeV was produced at Saclay in 1980s
Beam of 1 µA was used for SLC (120 Hz)
SLAC positron damping ring up to 1.2 GeV, 200 mA
DORIS
DAΦNE
VEPP-3 energy of 0.5-2 GeV, 50 mA
26
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Where to find a positron beam? A beam of 25 nA 400 MeV was produced at Saclay in 1980s
Beam of 1 µA was used for SLC (120 Hz)
SLAC positron damping ring up to 1.2 GeV, 200 mA
DORIS
DAΦNE
VEPP-3 energy of 0.5-2 GeV, 50 mA
27
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Concept of an experiment with a positron beam
28
electron
positronphoton
U boson
!"cm
electron
positronphoton
!"cm
photon
a)
b)
[MeV] !E0 50 100 150 200 250 300 350 400 450 500
]-1
s•pe
r 5 M
eV [
pho
tons
R
ate
210
310
410
o=60
CM !"
o=120
CM !"
Kinematics
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Concept of an experiment with a positron beam
29
500 MeV beam
Proposal of an experiment at VEPP-3: BW, Nikolenko, Rachek, arXiv:1207.5089
DETECTORREGION 2
DETECTORREGION 1
T
W1
W2
RF Cavity
Q1 Lens Q2 LensS
extu
pole
Target
6 m0 4 m2 m 8 m
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Experimental layout
30
Le+e− ∼ 1032
2.6!" =
o
!"4.5=
o
o
Pu
mp
2,3
Sex
tup
ole
Val
ve
Pum
p 4
Pu
mp
1
Val
ve
Photon Detector
Q3Q2
D3
D2
Q1
D1
Sandwich
Co
ld H
ead
Pump 5
217 cm
10.7o
Storage Cell
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Basic QED: e+e- → γ γ (mono-energetic) Search for : e+e- → γ U (peak below main)
Basic QED: e+Z → γ (smooth brems.)
The photo-production processes
• Detect γ at fixed angle with the beam:
reconstruct the mass • Variation with the angle: control systematic
• Target Z Hydrogen vs. 12C
31
[MeV]!E50 60 70 80 90100 200 300 400
[de
g]!
"
1
2
3
4
5
6
7
8
1
10
210
310
410
510
gamma background
[MeV]!E50 60 70 80 90100 200 300 400
[de
g]!
"
1
2
3
4
5
6
7
8
=15 MeVA'
A' for M! #
--+e+e
! ! #--+e
+e
! H + e#+H+e
! H + e#+H+e
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Positron beam on internal Hydrogen target
32
Anti-coincidence with the positron counters
reduce QED background
e+E = 450 MeV
e+ = 1.5oe+E = 100 MeV
e+ = 4.5o
e+ = 1.5o
e+ = 4.5oSandwich #1
Sandwich #2
vacuum chamber
400
70
Physics background is the bremsstrahlung radiation
[MeV]Threshold energy 0 50 100 150 200 250
]-1
s•[ p
hoto
ns
Rat
e
410
510
610
710 total
o- 4.5o = 1.5! "
-1s-2 cm32= 500 MeV L = 10+e EBremsstrahlung Rate -1s-2 cm32= 500 MeV L = 10+e EBremsstrahlung Rate
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Kinematical correlation
33
[deg] LAB!"
1 1.5 2 2.5 3 3.5 4 4.5 5
[M
eV]
LAB
!E
0
50
100
150
200
250
300
350
400
450
500
=10 MeV U
M
=15 MeV U
M
=20 MeV UM
!!
LAB!E
σ = πr2e
γ+· (ln 2γ+ − 1)
NUγ = 2α�
α· Nγγ
The U/A’ mass resolution ~ 3%
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Positron beam on internal Hydrogen target
34
[MeV]!E60 70 80 100 200 300 400 500
Rat
e p
er 5
MeV
, [H
z]
-310
-210
-110
1
10
210
310
410
510
[MeV]!E60 70 80 100 200 300 400 500
Rat
e p
er 5
MeV
, [H
z]
-310
-210
-110
1
10
210
310
410
510 + X! " + H +e o-0.8o = 0.4!#
o-2.0o = 1.6!#o-3.2o = 2.8!#o-4.4o = 4.0!#o-6.4o = 6.0!#
Projected event rate
A bump is e+e-2γ
[MeV]!E60 70 80 100 200 300 400 500
Rat
e p
er 5
MeV
, [H
z]
-310
-210
-110
1
10
210
310
410
510
[MeV]!E60 70 80 100 200 300 400 500
Rat
e p
er 5
MeV
, [H
z]
-310
-210
-110
1
10
210
310
410
510 + X! " + H --e o-0.8o = 0.4!#
o-2.0o = 1.6!#o-3.2o = 2.8!#o-4.4o = 4.0!#o-6.4o = 6.0!#
Projected for an electron beam for systematic check
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Photon detector
35
Potential source of crystals:
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
VEPP-3 operation during ���Two-Photon Exchange experiment
36
01:00 02:00 03:00 04:00 05:00 06:00 07:00
Lif
eti
me, s
210
310
410
510
electrons positrons lifetime
VEPP-3: experiment E = 1600 MeV November 22, 7:00
I = 35.6 mA LT = 1039 s
Cu
rren
t, m
A
0
10
20
30
40
50
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Projected sensitivity in the parameter space
37
-210 -110 1
-1010
-910
-810
-710
-610
-510
-410
BaBar
MAMIKLOE
ea
TestAPEX
Full
HPSE774
E141
E137
DarkLight
VEPP3
A' is 'welcome'µa
A' is excludedµa
(GeV)Um-210 -110 1
!'/!
-1010
-910
-810
-710
-610
-510
-410
Projected sensitivity for the VEPP-3 measurement at Lep =1032 cm-2/s (aver. current of 25 mA) in the six-month run
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Projected sensitivity in the parameter space
38
Projected sensitivity for VEPP-3 (at 500 MeV) measurement at Lep =1032 cm-2/s (aver. current of 25 mA) in the six-month run
- - - with 5 GeV beam
These searches are sensitive to “invisible”
-210 -110 1
-1010
-910
-810
-710
-610
-510
-410
BaBarKLOE
ea
DarkLight
VEPP3
A' is 'welcome'a
A' is excludeda
(GeV)Um-210 -110 1
'/
-1010
-910
-810
-710
-610
-510
-410
ae DarkLight ( to “invisible”)
Y. Kahn, J. Thaler, arXiv:1209.0777
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
Options for an e+e- experiment at low s
A “very” low energy, s1/2 ~ 30-100 MeV
a) 15 MeV x 15 MeV e+e- collider =>
b) Sliding beams of e+e- (500 MeV x 500 MeV at 25o)=> Project needs a specialized accelerator with two rings
c) Current approach is a positron beam + atomic electrons
39
L ∼ 1024
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013
A collider scheme for an e-e+ experiment at low s
40
s = (p+µ + p−µ )2
E+E−(1− cos θ+−)
L of 1033 at 1 GeV allows the L =1032 at s=100 MeV,
Angle is of 25 degrees between the beams will allow a U boson search with mass up to 100 MeV
L ∝ (1− cos θ+−) W.Pauli, 1933
Sliding beams
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 41
Summary
Search for the A’/U boson in the photon recoil spectra is possible using a positron beam and internal hydrogen target in the 500 MeV storage ring.
Available luminosity (~1032) allows a 10-100+��� improvement over the (g-2) limit in mass range 7-15 MeV. The range could be extended to 50 MeV with 5 GeV beam.
A e+e- collider based on a sliding scheme could be a U boson factory for the low mass range.
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 42
Luminosity of the colliders
from W. Panovsky’s article in BEAM LINE
For Ecm=100 MeV L ∼ 1026 − 1029cm−2/s
Dashed line isL ∝ E2
cm
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 43
Luminosity using initial state radiation
∆L ∝ L × ∆ssmax
s ∼ 4E+ · (E− − Eγ)
when smax = 10 GeV and ∆s ∼ 100 MeV (APEX)∆L ∼ 10−4L
B. Wojtsekhowski seminar at LNF, Frascati, Italy, Sept. 26/2013 44
BABAR search using initial state radiation 2
Even
ts p
er 1
0 M
eV/c
5000
10000 (a)
0
J/(2S)
)2Candidate mass (GeV/c0 2 4 60
1000
2000
3000 (b)
J/
(2S)
PRL 107, 221803 (2011) Search for Hadronic
Decays of a Light Higgs Boson
in the Radiative Decay