a new dark photon search p-division seminar los alamos national laboratory roy j. holt physics...
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A new dark photon search P-Division Seminar Los Alamos National Laboratory
Roy J. HoltPhysics DivisionArgonne National Lab
26 February 2015
What’s the matter?
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Dark matter is:
•a most profound mystery of modern physics
•a central element of cosmology and astronomy
•most of the mass of the Universe
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Intensity Frontier Workshop, Dec 2011, www.intensityfrontier.orgConvenors for nuclear physics: Haxton, Lu, Ramsey-Musolf
Priorities according to Nima Arkani-Hamed,Institute for Advanced Study (Princeton)
Dark Matters
Dark matter exists and interacts by gravity– Rotation curves of galaxies, gravitational lensing– Cluster galaxies– …
Is there a Standard Model connection to the dark sector?– Does dark matter interact in any other way than by gravity?
Dark photons might provide a “portal” to the dark sector U(1) extensions of the Standard Model are natural
– Pseudoscalar U(1) axions (strong CP problem)– Vector U(1) dark photons
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Rotation curves of galaxies
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F. Zwicky, ApJ 86 (1937) 217, V. Rubin et al, ApJ 238 (1980) 471Figure credit: H. Merkel
Dark photons explain mass extinctions?
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FIG. 2: Our Solar System orbits around the Milky Way’s center, completing a revolution every 250 million years.Along this path, it oscillates up and down, crossing the galactic plane about every 32 million years. If a dark matter diskwere concentrated along the galactic plane, as shown here, it might tidally disrupt the motion of comets in the Oort cloudat the outer edge of our Solar System. This could explain possible periodic fluctuations in the rate of impacts on Earth.(APS/Alan Stonebraker)L. Randall and M. Reece, PRL 112 (2014) 161301; J. I. Read et al, Mon. Not. Roy. Astro. Soc 389 (2008) 1041
Very active field with many new results
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Positron observations from satellite data
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M. Aguilar et al., PRL 113 (2014) 121101
Positron excess from AMS-02
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typical theory Expectation
Pulsars?
M. Aguilar et al., PRL 113 (2014) 121101
Positron excess decreases at high energy
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Consistent with ~ 1 TeV dark matter particles annihilating?
S. Ting, CERN press release forAMS collaboration, Sept. 18, 2014
No anti-proton excess
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O. Adriani et al., Nature 458 (2009) 607
Gamma-ray excess from the Galactic Center
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P. Agrawal et al., arXiv: 1404.1373T. Daylan et al, arXiv: 1402.6703Hooper and Linden, PRD, arXiv:1110.0006
B. D. Fields, S. L. Shapiro, J. Shelton,PRL 113 (2014) 151302
The Economist, April 12, 2014
• Not yet explained by known astrophysical sources
• Can be explained by dark matter annihilation
• What about a black hole spike?
Sagittarius A*Supermassive blackhole at GC
Dark matter search strategies
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SM
SM
Direct production:LHC
Direct search:CDMS, DAMA, XENON, CREST, LUXCOUPP, PICO, MiniCLEAN, …
Indirect search:PAMELA, Fermi, HESS, ATIC, AMS-02, WMAP
New Force ?
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Standard Model
Quarks, leptons
g W Z
Standard Model
Quarks, leptons
g W Z
Hidden Sector
dark matter
A’
Hidden Sector
dark matter
A’
Known forces Dark force?
SU(3)C x SU(2)W x U(1)Y U(1)’
Strong weak EM
Dark photons might provide a portal to dark matter
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Standard Model
Quarks, leptons
g W Z
Standard Model
Quarks, leptons
g W Z
Hidden Sector
dark matter
A’
Hidden Sector
dark matter
A’
B. Holdom, PLB 166 (1986) 196J. D. Bjorken et al, PRD 80 (2009) 075018
~ 1E-2 to 1E-8 from loops of heavy particles
•Discovery of dark photons would be revolutionary•Dark photons could explain:
• positron excess in high energy Cosmic rays• Gamma ray excess near Galactic Center• (g-2) of the muon anomaly• …
Muon (g-2)
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16H. Davoudias et al, PRD 89 (2014) 095006
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Dark Photons at RHIC ?Muon g-2 experiment (E821) has 3.6 result beyond the Standard Model
PHENIX has excellent dark photon search capabilities
No dark photon signal seen
PHENIX upper limit, plus othersrules out dark photons withno hidden sector decays as g-2 explanation
A. Adare et al, arXiv:1409.0851
The search is on …
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Courtesy: R. Milner at the Fundamental Interactions Town Meeting, Chicago, Sept. 28-29, 2014
XA’
(also ALICE)
Possible production mechanisms for dark photons
Bremsstrahlung
0, , … decay
Drell-Yan (J.-C. Peng, S. Prasad)
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A’
p
pl+
l-
Dark forces: decay
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Courtesy: N. Toro
~ 1E-2 to 1E-8 from loops of heavy particles
Most of the relevant parameter space is not shown
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Plot: W. Marciano
Non-Standard Model Higgs decays at the LHC
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arXiv: 1409.0746
Hidden Lightest Stable ParticleHidden
fermion
Hiddenscalar
BR(H -> 2d) = 5 -40% ??
Main injector at FNAL - 120 GeV protons
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Fermilab E906/SeaQuest CollaborationAbilene Christian University
Ryan Castillo, Michael Daugherity, Donald Isenhower, Noah Kitts, Lacey Medlock, Noah Shutty, Rusty Towell, Shon Watson,
Ziao Jai Xi
Academia SinicaWen-Chen Chang, Ting-Hua Chang, Shiu Shiuan-Hao
Argonne National LaboratoryJohn Arrington, Don Geesaman*, Kawtar Hafidi,
Roy Holt, Harold Jackson, David Potterveld, Paul E. Reimer*, Brian Tice
University of ColoradoEd Kinney, Joseph Katich, Po-Ju Lin
Fermi National Accelerator LaboratoryChuck Brown, Dave Christian, Su-Yin Wang, Jin-Yuan Wu
University of IllinoisBryan Dannowitz, Markus Diefenthaler, Bryan Kerns, Hao Li, Naomi C.R Makins, Dhyaanesh Mullagur R. Evan McClellan,
Jen-Chieh Peng, Shivangi Prasad, Mae Hwee Teo, Mariusz Witek, Yangqiu Yin
KEKShin'ya Sawada
Los Alamos National LaboratoryGerry Garvey, Xiaodong Jiang, Andreas Klein, David Kleinjan,
Mike Leitch, Kun Liu, Ming Liu, Pat McGaughey
Mississippi State UniversityLamiaa El Fassi
University of MarylandBetsy Beise, Yen-Chu Chen, Kazutaka Nakahara
University of MichiganChristine Aidala, McKenzie Barber, Catherine Culkin, Vera
Loggins, Wolfgang Lorenzon, Bryan Ramson, Richard Raymond, Josh Rubin, Matt Wood
National Kaohsiung Normal UniversityRurngsheng Guo, Su-Yin Wang
RIKENYoshinori Fukao, Yuji Goto, Atsushi Taketani, Manabu Togawa
Rutgers, The State University of New JerseyRon Gilman, Ron Ransome, Arun Tadepalli
Tokyo TechShou Miyaska, Kei Nagai, Kenichi Nakano, Shigeki Obata,
Florian Sanftl, Toshi-Aki Shibata
Yamagata UniversityYuya Kudo, Yoshiyuki Miyachi, Shumpei Nara
*Co-Spokespersons
5 national labs, 11 universities!
Drell-Yan measurements on the proton and deuteron
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ubar > dbar
J.-C. Peng et al, PLB 736 (2014) 411
Revealing the “Peng effect”
Ideal beam stop experiment
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Detector is well-shielded from Standard Model background
Vertex for pair production is downstream from the target
mA’ = invariant mass of
Resonance production
target shield pair spectrometer
High energy
Proton beam
A’
l+
l-
SeaQuest Experiment
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Lint(Fe) = 0.17 m = target lengthShield (Fe) = 4.8 m – <Lint> Fiducial region = LFe + 0.95 m
Figure credit: Kenichi Nakano, Shou Miyasaka
Solid Fe magnet – thanks to DOE for fundingand for lack of funding
1-m Fe
Branching ratios for A’ decay assuming no hidden sector decays
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D. Curtin, et al, arXiv 1312.4992v2R. Essig, priv. comm. (2014)
SeaQuest Experimental Setup
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•Spectrometer commissioned in March 2014•Experiment will run for at least another year
followed by LANL’s E1039 experiment•Nearly ideal for a dark photon search
LANL LDRD -> more ideal
Thanks to R. Evan McClellan
Preliminary
Decay length vs. mass, energy,
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J. D. Bjorken et al, PRD 80 (2009) 075018
Charged particle production at 120 GeV
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S. Mahajan, R. Raja, arXiv:1311.2258; FNAL E907, MIPP
= 2.2 b for all charged particle productionAssume that ’s represent 90% of charged particles,
and production is 1/10 of this value.
Resonance production
Proton bremsstrahlung
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p
p’l+
l- + p -> ’+ p’
Generalized Fermi-Williams-Weizsacker approximation
J. Blumlein, J.Brunner, PLB 731 (2014) 320
z = (Ep – Ep’)/Ep; s = 2MEp; s’ = 2M(Ep – EA’)
Proton bremsstralung flux
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= 1
Worldwide search for dark photons (exclusion plot)
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JLab projections
FNAL E906SeaQuestprojectionspreliminary
Plot credit: A. Tadepalli
2E12 ppp100% efficiency200 days10 event contours
How would 50 events with S/B = 1:1 appear?
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SeaQuest Projections preliminary
With e+e- detection
Dark Matter can come in different shades of gray?
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Slide credit: S. Gardner
The visible and hidden sectors can mix in different ways…
[Note Batell, Pospelov, and Ritz, PRD 80 (2009) 095024 for a review re fixed target expts.]Here we consider a non-Abelian (gluon) portal [Baumgart et al., JHEP 0904, 014 (2009); Gardner and He, PRD 87 (2013) 116012]The “shining through walls” design – unique to Seaquest – makes this possible , to yield, e.g., via a “minimal” decay….
With detection
SeaQuest Projections preliminary
Production [
First look at background events
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Monte Carlo: p - inelastic scattering Actual data - 8 hours
Fiducial region
Fiducial region
Thanks to Kun Liu09 May 2014Tracker is not yet optimized for dark photonsTrigger 57, not optimal for dark photons
Second look for possible events
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Runs 8919-9117 ~90 hours,
Very preliminary
Thanks to R. Evan McClellan20 October 2014Same tracker as beforeTrigger 59
Distance (cm)
Distance (cm)
Summary
Existence of dark matter is a reason to investigate new forces New initiative for SeaQuest - search for dark photons Leverage the newly commissioned spectrometer and 120 GeV
proton beam at FNAL Ultimate goal is to discover dark photons and provide a window
into dark matter in a laboratory setting Detecting e+e- and in SeaQuest would greatly extend the
reach, possibly including some non-Abelian dark forces Next few years: a discovery or a large excluded region of
parameter space Don’t be afraid of the dark!
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Extra slides
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Confidence levels
CLs or Becker method P(n,x) is the Poisson probability to observe n events for a mean value of x N = number of event observed, b = background events, s = signal
N=1, b=0.7, 95% CL exclude signal of 4.5 events, proton bremsstrahlungJ. Blumlein, J.Brunner, PLB 731 (2014) 320
N=5, b=3.5, 95% CL exclude a signal of 7.3 events, 0 decayJ. Blumlein, J.Brunner, PLB 701 (2011) 155
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Mass distribution for events 3-5 m downstream
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Thanks to R. Evan McClellan
Mass (GeV)
Even
tsVery preliminary
More assumptions
Beam intensity – 6 x 1012 protons per minute Beam protons rejected - 40% Dark photon acceptance – 50% Dead time - 15% Target thickness – 1 interaction length of Fe Dimuon tracking efficiency – 50% Time – nominal year - 200 days Minimum number of dark photon events – 10 Signal to background – 1:1 Confidence level - 95%
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Drell-Yan is the best way to measure sea-quark distributions
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What is the A dependence of antiquarks?
Longer term: Polarized FNAL/target, J-PARC
Commissioning completedMarch 2014