the search for an electric dipole moment of the neutron at psi jochen krempel eth zürich 1jochen...

nEDM data blinding

The search for an electric dipole moment of the neutron at PSIJochen KrempelETH Zrich1Jochen Krempel14.10.2015 FFK BudapestOn behalf of the nEDM collaboration at PSI

13 Institutions 7 Countries48 Members11 PhD students

The collaboration

14.10.2015 FFK BudapestJochen Krempel2

The collaboration consists of 13 institutions in seven countriesAltogether we are 48Of which 11 are doing there PhD thesis on the project.2OutlineShort MotivationPrinciples of nEDM measurementUCN SourceExperiment & upgradesData blindingPerformanceOutlook3Jochen Krempel14.10.2015 FFK Budapest14.10.2015 FFK Budapest4Jochen Krempel

Baryon Asymmetry of the Universe

Sakharov 1967:CP-violation[JETP Lett. 5 (1967) 24]We live in a matter dominated universe

Observed (WMAP)Expected (SM)

[Riotto et al. 1999 Ann.Rev.Nucl.Part.Sci. 49 ][E. Komatsu et al. 2011 ApJS 192]B-violationC & CP-violationnon-equilibrium14.10.2015 FFK Budapest5Jochen KrempelEDM violates CPA permanent EDM of any fundamental particle violates CP

PCTHaving T-violationAnd assuming CPT invariance CP must be violatedNote: magnetic field is a pseudo vector (as spin) m does NOT violate CP

Magnetic field or m is not necessary for CP violation. But a nice tool to control the spin.Different coupling to external fields Different particleHowever, a neutron is different from anti-neutron. Use alternative way

14.10.2015 FFK Budapest6Jochen KrempelHistory of nEDM

Lamoreaux, Golub in Lepton dipole momentsRoberts, Marciano (eds.) 2010 World Scientific Publishing current best nEDM limit:dn < 2.910-26 e cm (90% C.L.)C.A.Baker et al., PRL 97, 131801 (2006)Sensitivity goals at PSI Intermediate: dn < 5 x 10-27 e cm (95% C.L.) Final: dn < 5 x 10-28 e cm (95% C.L.)A. Serebrov ILL GatchinaTUM ILL RALORNLTRIUMFF. Piegsa ESSPrinciples of nEDM measurementHow to measure precession?pickup coil not enough signal

Measure polarization of neutrons

2 sequential measurements E,B (anti-)parallel Measure precession frequency twice7Jochen Krempel14.10.2015 FFK Budapest

Principles II: Ramsey technique

8Jochen Krempel14.10.2015 FFK Budapest

Spin up neutrons

p/2 flip pulse

Free precession

p/2 flip pulse

ExternalclockNeutronclock

aDn

Spin analyser -> count rate-Pi/2 flip shifted in phase, not fully spin downPhase shift frequency shiftscan frequency observe Ramsey fringe = interference between 2 clocks, beating of sound, moireEDM signal is frequency shift (horizontal shift of the pattern)We measure only 4 working points in the most sensitive regionDo also with SpinDown for more statisticsSensitivity equation

8SensitivitySqrt(N) and T compete (repetition rate). T is more important Last Decades: Trap better than beamTrap walls limit EStorage time t Long T = low NDepolarization rate t2 Long T = low a14.10.2015 FFK BudapestJochen Krempel9

14.10.2015 FFK Budapest10Jochen KrempelThe apparatus

~1m diameter x 1.5m length50cm diameter x 12cm heightultracold neutrons - UCNUCN < 300neV ~ 8m/s ~ 3 mK > 50 nm !

thermal (25 meV) 2200 m/s 300 K 0.18 nm

cold (5 meV) 1000 m/s 60 K 0.4 nm

UCN (< 260 neV) < 7 m/s 0.003 K > 50 nm hence the name

Neutrons with Ekin < 300 neV are storeablee.g. air molecules at 20 C: ~400 m/sE. Fermi, 1946 , Ya. B. Zeldovich Sov. Phys. JETP 9, 1389 (1959)

vnvCvn>vCvnsurface description via amaterial optical potentialDensity is low no particle-particle interactionElastic collisions with walls no thermalization14.10.2015 FFK BudapestJochen Krempel11Ultracold neutrons (UCN) can be stored- storage properties arematerial dependent-Ni, Ni58, Be, DLC, steelGravityMaterial Magnet for polarized UCN 60 neV T-1magneticVm = -mBVg = mnghgravitation100 neV m-1< 250neV300neV = 5 T one polarization300neV = 3m14.10.2015 FFK BudapestJochen Krempel12

Neutron production via proton spallation on leadUCN SourceProton Accelerator590 MeV Cyclotron2.2 mA beam current nEDM 2 experimental areas / 3 beamlineskicker to UCN


Sketch of the PSI UCN sourcepulsed1.3 MW p-beam590 MeV, 2.2 mA,1% duty cyclespallation target (Pb/Zr)(~ 8 neutrons/proton)heavy water moderator thermal neutrons3.6m3 D2Ocold UCN-converter~30 dm3 solid D2 at 5 Ktank7 mDLC coatedUCN storage vesselheight 2.5 m, ~ 2 m3

UCN guides towardsexperimental areas8.6m(S) / 6.9m(W)SV-shuttercryo-pump14.10.2015 FFK BudapestJochen Krempel14

Measurement in area Westwith detector at beam-portpilotpulsefillingstorage vesselemptyingstorage vesselup to 2x107 UCN /pulseclosingshutter

typical exp filling time ~30s15

UCN-Source progress in 2015Melting + re-freezing (4h every 4 days)Increase duty cycle (average current)14.10.2015 FFK BudapestJochen Krempel16Magnetic field stabilityE polarity change every ~5 hours.Keep B-field stablePassive mu-Metal shield 4 layers ~ a few * 1000 suppressionActive Coils (SFC)Measure fluctuationsHg co-magnetometerCs magnetometers


14.10.2015 FFK Budapest18Jochen KrempelThe apparatus - magnetic shielding

1uT

SFC - part I6 rectangular coils6m * 8m, 20 windings10 x 3 axis Fluxgate sensors

earth field compensation /sultan field compensation

gradient compensation not yet fully possible (lack of number of coils)staticstabilisation over timePair wiseusing inverse matrix

Sensor selection14.10.2015 FFK Budapest19Jochen KrempelResponse function -> matrixPseudo inverseNeed to regularize19

SFC - part II>5x shielding 5 .. 5000 s of real perturbations

14.10.2015 FFK Budapest20

Afach et al., J. Appl. Phys. 116, 084510 (2014) Jochen Krempel14.10.2015 FFK Budapest21Jochen KrempelThe apparatus Hg co magnetometer

Hg co-magnetometer14.10.2015 FFK BudapestJochen Krempel22

UCNHgCentre of mass offset: ~2mmmismatch in case of dBz / dz8HzCs-magnetometer arrayPump and probe at 45t about 20msExtra cell, special coating.High statistics High bandwidth (wL=3.5kHz)Array of 16 sensorsHV-versions included dB / dz information

Vector-information (prototype)14.10.2015 FFK BudapestJochen Krempel23

14.10.2015 FFK Budapest24Jochen KrempelThe apparatus Hg co magnetometer

132kV / 12cm

Improve Depolarization rate14.10.2015 FFK BudapestJochen Krempel25

Depolarization rate t2 Long T = low a

33 Trimcoils to tune the field. But how?

Not published yet.Use Cesium-array, do some fancy things,get Trimcoil settings, Enjoy!

R-curve analysisScan actively dB/dzby applying TrimCoils


B0 up B0 downPrior to Cs-magnetometer array the only way to determine 0-gradient.

Gyro magnetic ratio

S. Afach et al., PLB 739 (2014) 128


B0upfEarth

Earth rotation correction

14.10.2015 FFK BudapestJochen Krempel2828Spin-echo spectroscopy

A spin-echo recovers energy dependent dephasing forT = 2t1 in a magnetic field withnegative vertical gradient.

gz14.10.2015 FFK BudapestJochen Krempel29Estimation of UCNenergy spectrumAccess to vertical gradient (absolute value)

Spin-echo results

S.Afach et al., accepted by PRL( 02. October 2015), arXiv:1506.00446


R-curve revisitedPolarization and R-curve using UCN spin-echo spectrum match data taken at T=180sGravitational depolarization of ultracold neutrons: Comparison with dataS. Afach et al.Phys. Rev. D 92, 052008 Published 22 September 201514.10.2015 FFK BudapestJochen Krempel31

Systematic effects14.10.2015 FFK BudapestJochen Krempel32

16 CsM arrayHigh precisionfield mappingWhy blindingAvoid psychological bias during data analysisExperimenters bias is defined as the unintended influence on a measurement towards prior results or theoretical expectations.Which cut to applyWhen to stop analysis/searching for bugs"We're more than one sigma from zero; we have to look at it some more, because we must be doing something wrong..."

Outside reputation some secrecy is necessary, simply trusting everybody is not enough.

Do NOT protect against: Criminal energy, e.g. somebody installing spyware on DAQ computerJR Klein A RoodmanBLIND ANALYSIS IN NUCLEAR AND PARTICLE PHYSICSAnnual Review of Nuclear and Particle Science 2005Vol. 55: 141-163 DOI: 10.1146/annurev.nucl.55.090704.151521arXiv:physics/0312102v1Blind Analysis in Particle PhysicsAaron Roodman

14.10.2015 FFK BudapestJochen Krempel33Blind analysis: Hide results to seek the truth R. MacCoun, S. Perlmutter Nature 526, 187189 (08 October 2015) doi:10.1038/526187a

Mention 56 kinds of biases in medical research

We fix only one, and are scared to not introduce another one.33Blinding offsetMany experiments have blinding factor

nEDM measures value + uncertaintyFrom that upper limit is derivedWe blind the raw data by shifting the value Blinding offset14.10.2015 FFK BudapestJochen Krempel34Why is blinding so difficultEasy concept:Modify frequency of neutron spin flip (synchronous to HV-polarity)Must not influence measurement Fear of systematic effects is largeIndependently advised by review committeeWrite down a false frequencyImmediately visible in co-magnetometersFake the reading of a co-magnetometerImpossible to do consistently for Hg and Cs immediately visible35Jochen Krempel14.10.2015 FFK BudapestHow do we blind I36Jochen Krempel14.10.2015 FFK Budapest

ni / Shift neutron counts from one detector into the other-> SpinDown becomes SpinUp (or vice versa)Have to follow Ramsey curveHave to know phase/frequency of spin flipHave to know E-fieldHave to know B0 direction, Detector config, spinFlipper 1 (per experiment)problem with alpha and N average unknown before end of run

36

How de we blind II14.10.2015 FFK BudapestJochen Krempel37

ni / How do we blind III


Known (because chosen)phase/frequency of spin flipE-fieldsign of B0 direction,sign of Detector configurationsign of SpinFlipper 1

N and a are fitted per run (~1day)

mention Poisson38Secrecy of data filesRaw data (secret) + blinded data (public)Backup scheme:

Encrypt secret data with RSA (asymmetric)Use public key for encryptionPrivate key is kept in sealed envelopeDo not trust encryption -> keep additional copy (NOT encrypted) at hidden place39Jochen Krempel14.10.2015 FFK Budapest

Slow controlMain DAQNeutronIntern PSIPSI -AFSFrancePSI tapeGRIS PolandPerformance 201514.10.2015 FFK BudapestJochen Krempel40

Performance 201514.10.2015 FFK BudapestJochen Krempel41

Pseudo magnetic field from aspin-dependent exotic force

Axion Windowwhere UCN are a sensitive probe

Constraining interactions mediated by axion-like particles with ultracold neutronsPhysics Letters B Volume 745, 18 May 2015, Pages 5863 10.1016/j.physletb.2015.04.024Poster by Beatrice Franke42Light axions axion wind14.10.2015 FFK BudapestJochen Krempel43

Y. V. Stadnik and V. V. Flambaum PHYSICAL REVIEW D 89, 043522 (2014)The future - n2EDMDouble Chamber E-B parallel antiparallel at same timeHorizontal guide Higher N due to better use of spectrumHigher EMore Cs magnetometers (vector information)14.10.2015 FFK BudapestJochen Krempel44SummaryThe collaboration produced many papers during the last year.Since August 2015 very stable running with best daily sensitivity world wide.Systematic effects studied in detail.14.10.2015 FFK BudapestJochen Krempel45AcknowledgementsSpecial thanks for slides to Philipp Schmidt-WellenburgBernhard LaussMartin FertlGeorg BisonMicha RawlikDieter Ries

The whole collaboration.14.10.2015 FFK BudapestJochen Krempel46

Thank youfor your attentionBackup Slides14.10.2015 FFK BudapestJochen Krempel47Simultaneous spin detection

~20% increase in sensitivity(for 2014)

sequential A device for simultaneous spin analysis of ultracold neutrons EPJ A Accepted 12 October 201548Cs OPM

Servo14.10.2015 FFK BudapestJochen Krempel49UCN Production Conventional

300 K30 K

10-13 F0[cm-2s-1] cm-3

r(UCN)=70x10-13 F0 [cm-2s-1] cm-3Using an adequate moderator and extracting the low-energy tail of theMaxwell-Boltzmann distribution:(first UCN observed in the 1960 - Russia)F0ModeratorExperimentliquiddeuterium14.10.2015 FFK BudapestJochen Krempel50

4HeF. Atchison et al., PRL99(2007)262502D2C.A. Baker et al., PLA308(2003)67dispersion relation

How can we obtain more UCN ?Superthermal UCN production:Golub & Pendlebury

14.10.2015 FFK BudapestJochen Krempel51Hg-Level Scheme14.10.2015 FFK BudapestJochen Krempel52

Allan Deviation with VCsM

14.10.2015 FFK BudapestJochen Krempel53Secrecy of blinding offsetBlinding program needs to know itRandomly generate offset, store it with (2nd) public keyprivate key is injected into blinding program during compile processBlinding offset is never written in clear text (nobody can accidentally read it)Blinding code can be modified at any time and recompiled- one trustful person necessary to keep private key54Jochen Krempel14.10.2015 FFK BudapestSecrecy implementationStep 0) Get their public keyopenssl rsa -in id_rsa -pubout -outform pem > id_rsa.pub.pemStep 1) Generate a 256 bit (32 byte) random keyopenssl rand -base64 32 > key.binStep 2) Encrypt the key (asymmetrically)openssl rsautl -encrypt -inkey id_rsa.pub.pem -pubin -in key.bin -out key.bin.enc Step 3) Actually Encrypt our large file (symmetrically)openssl enc -aes-256-cbc -salt -in SECRET_FILE -out SECRET_FILE.enc -pass file:./key.bin Step 4) Put key.bin.enc and SECRET_FILE.enc to ArchiveDecryption (in 2 years)openssl rsautl -decrypt -inkey id_rsa.pem -in key.bin.enc -out key.bin

openssl enc -d -aes-256-cbc -in SECRET_FILE.enc -out SECRET_FILE -pass file:./key.bin55Jochen Krempel14.10.2015 FFK BudapestBACKUP RSA algorithmhttps://de.wikipedia.org/wiki/RSA-Kryptosystem Calculate private keyChose 2 large prime numbers p = 11 and q = 13 RSA-Modulus is N = p * q = 143Euler's totient function phi(N) = phi(143) = (p-1)(q-1) = 120Chose e coprime to 120. We chose e = 23.

e = 23 and N = 143 are the public key.Calculate public key (Inverse of e): e * d + k * phi(N) = 1 = ggT(e,phi(N)) (Greates Common Divisor)23 * d + k * 120 = 1 = ggT(23,120). Extended Euclidean algorithm d=47 and k=-923 * 47 + (-9 )* 120 = 1d=47 is the secret key, k can be disposedencryption m=7 with public key (e,N) (m < N)c = m ^ e mod N 7 ^ 23 mod 143 = 2decrypt m = c ^ d mod N 2 ^ 47 mod 143 = 756Jochen Krempel14.10.2015 FFK Budapest

the search for an electric dipole moment of the neutron at psi jochen krempel eth zürich 1jochen...

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