Axion-like particles from proton beam dumps

Transcription

1 Axion-like particles from proton beam dumps Babette Döbrich (CERN) BCTP Bonn, March 2016 Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

2 Disclaimer/Summary [Bethe workshop anno 2016] [SPS control room anno 1977] beam dump searches for axions might evoke a feeling of time travel to parts of the audience see, e.g. dump chapter in [Rosenberg/Bibber Phys. Rept. 325] today s physicists regain interest for very weakly coupled with masses (well) below the need of highest-energy accelerators ( low energy frontier ) e.g. proposal for a dedicated dump-search at SPS ( SHiP, mainly meant for heavy neutral leptons) as incentive to look at prospects specifically for Axion-like particles (and others), maybe even at existing facilities ( SHiP is still to be approved and built) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

3 Brief Intro: Axions vs ALPs [figure courtesy of J.Jaeckel] new physics is somewhere! could be at high mass (traditional & successfull & motivated paradigm) could be at low mass and very small couplings (pragmatic & very motivated paradigm) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

4 Brief Intro: Axions vs ALPs [figure courtesy of J.Jaeckel] new physics is somewhere! could be at high mass (traditional & successfull & motivated paradigm) could be at low mass and very small couplings (pragmatic & very motivated paradigm) focus on axions coupled predominantly to photons (actually, many more possibilities!) [from : Dark Sectors and New, Light, Weakly-Coupled Particles] Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

5 Brief Intro: Axions vs ALPs cleans (detergent!) finetuning of focus on axions coupled predominantly to photons (actually, many more possibilities!) pseudoscalar axion solves strong CP problem as PNGB of Peccei-Quinn symmetry [Peccei, Quinn, 77; Weinberg, Wilczek, 78] Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

6 Brief Intro: Axions vs ALPs [created through paperscape.org] an axion-like particle (ALP) is a general (pseudo-)scalar Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

7 Brief Intro: Axions vs ALPs [created through paperscape.org] Babette Do brich (CERN) an axion-like particle (ALP) is a general (pseudo-)scalar Axion-like particles from proton beam dumps BCTP Bonn, March / 21

8 Axion(-like) particles coupled to two photons Log Coupling [GeV -1 ] [adapted from , some things not up-to-date, sorry!] Helioscopes (CAST) SN γ-burst LSW KSVZ axion Haloscopes Vacuum Birefringence ADMX-HF ADMX e + +e - -> γ+inv. Solar ν HB Telescopes x ion X-Rays EBL Beam Dump SN1987a LEP BBN CMB Log Mass [ev] QCD axion: yellow band, ALPs possible (in principle) in all white regions colored is excluded Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

9 Axion(-like) particles coupled to two photons Log Coupling [GeV -1 ] [adapted from , some things not up-to-date, sorry!] Helioscopes (CAST) SN γ-burst LSW -12 Transparency hint WD cooling hint ALP CDM KSVZ axion Haloscopes Vacuum Birefringence ADMX-HF ADMX axion cdm e + +e - -> γ+inv. Solar ν HB Telescopes x ion X-Rays EBL Beam Dump SN1987a LEP BBN CMB Log Mass [ev] QCD axion: yellow band, ALPs possible (in principle) in all white regions colored is excluded interesting regions: cold Dark Matter (axion and ALP) some Astrophysical hints [better see Javi s talk] Hidden sector (mediators DM, dep. coupl.) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

10 Tackling ALPS at low and medium masses (below LHC) Vacuum Birefringence e + +e - -> γ+inv. Beam Dump LEP Log Coupling [GeV -1 ] Helioscopes (CAST) SN γ-burst LSW ALPS-II -12 Transparency hint WD cooling hint ALP CDM KSVZ axion Haloscopes YMCE IAXO ADMX-HF ADMX axion cdm Solar ν HB Telescopes x ion X-Rays EBL SN1987a BBN CMB Log Mass [ev] LSW, e.g. ALPS-II Helioscope e.g. IAXO Haloscope, e.g. ADMX Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

11 Tackling ALPS at low and medium masses (below LHC) Vacuum Birefringence e + +e - -> γ+inv. Beam Dump LEP high mass region? intense photon source? accelerate charged particles! Log Coupling [GeV -1 ] Helioscopes (CAST) SN γ-burst LSW ALPS-II -12 Transparency hint WD cooling hint ALP CDM KSVZ axion Haloscopes YMCE IAXO ADMX-HF ADMX axion cdm Solar ν HB Telescopes x ion X-Rays EBL SN1987a BBN CMB Log Mass [ev] and shield from backgrounds and highly charged particles fixed target/dump Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

12 ALP production in particle-on-target p Z a produce ALPs through different channels, but need clean prediction for S/B primarily: 1) Primakoff-like and 2) ALPstrahlung q q a perturbative calculation requires large p t Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

13 ALP production in particle-on-target photons soft in respective rest frames produce ALPs through different channels, but need clean prediction for S/B primarily: 1) Primakoff-like and 2) ALPstrahlung 1) perturbative & can have a coherent Z 2 enhancement simple atomic and nuclear form factors (resolve charged core but not the nucleon) + EPA (Weizäcker-Williams) blue shifted γs: energy for heavy ALPs Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

14 ALP production in particle-on-target produce ALPs through different channels, but need clean prediction for S/B primarily: 1) Primakoff-like and 2) ALPstrahlung 1) perturbative & can have a coherent Z 2 enhancement simple atomic and nuclear form factors (resolve charged core but not the nucleon) + EPA (Weizäcker-Williams) previous Primakoff ALP studies and madgraph MC ignore photon p t, ALP exactly on axis (θ = 0) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

15 Production cross-section for ALPs in p + N 10-1 θ θ Ea [GeV] m a = 50 MeV Ea [GeV] m a = 500 MeV log 10 dσ / de a dθ pb GeV log 10 dσ / de a dθ pb GeV assume 400GeV protons on a copper target & keep p t most ALPs produced at 20 mrad photon p t non-negligible! given any angle wrt beam axis, σ a distribution in θ and E a for each ALP mass we can retrace and predict a signal in an experiment (to see if it s worth doing) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

16 detector dumped MeV-GeV axion-like particles review N det ( N pot σ a/σ p exp D ) γβτ }{{} decay in vac ( exp D + L γβτ ) }{{} decay in detector decay length γβτ, ALP lifetime Γ = τ 1 = g 2 aγm 3 a/(64π) p absorber decay v. Z a D L R Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

17 dumped MeV-GeV axion-like particles review N det ( N pot σ a/σ p exp D ) γβτ }{{} decay in vac ( exp D + L γβτ ) }{{} decay in detector decay length γβτ, ALP lifetime Γ = τ 1 = g 2 aγm 3 a/(64π) exclusion through dumps g aγ [GeV -1 ] HB Y-> invisible e + e - -> inv. + γ Cosmo SLAC 141 CHARM SLAC 137 SN1987a LEP NuCal m a [GeV] early decay + rate POT E beam CHARM 400 GeV, N pot = on copper, D = 480m, L = 35m (off-axis: 7-12 mrad) NuCal 70GeV, N pot = on iron, D = 64m, L = 23m, on-axis 0-15 mrad SLAC141 9GeV, N eot = on tungsten, D = 35m SLAC137 20GeV, N eot = on aluminum, D = 200m estimates for CHARM and NuCal newly derived for pure γ [BD, Jaeckel, Kahlhoefer, Ringwald, Schmidt-Hoberg JHEP 1602, 018] Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

18 Extending the Axion-like-Particle reach at NA62? na62.web.cern.ch/na62/ NA62 currently taking data for measurement of K + π + ν ν at CERN SPS (400GeV protons) 1 m achromat Gigatracker Charged anti counter vacuum Large angle photon veto Spectrometer magnet CHOD RICH Liquid Krypton calorimeter Muon veto target tax CEDAR D 81m achromat collimator Large angle photon veto L 135m Straw chambers Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21 spectrometer IRC SAC

19 Extending the Axion-like-Particle reach at NA62? from target 400GeV p+ 75GeV K+ & more 75GeV NA62 currently taking data for measurement of K + π + ν ν at CERN SPS (400GeV protons) copper TAX after target 1 m achromat Gigatracker Charged anti counter vacuum Large angle photon veto Spectrometer magnet CHOD RICH Liquid Krypton calorimeter Muon veto target tax CEDAR D 81m achromat collimator Large angle photon veto L 135m Straw chambers Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21 spectrometer IRC SAC

20 Extending the Axion-like-Particle reach at NA62? from target 400GeV p+ 75GeV K+ & more NA62 currently taking data for measurement of K + π + ν ν at CERN SPS (400GeV protons) copper TAX after target can run in dump mode by closing TAX, γs not expected! 1 m achromat Gigatracker Charged anti counter vacuum Large angle photon veto Spectrometer magnet CHOD RICH Liquid Krypton calorimeter Muon veto target tax CEDAR D 81m achromat collimator Large angle photon veto L 135m Straw chambers Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21 spectrometer IRC SAC

21 Extending the Axion-like-Particle reach at NA62? Calorimeter hole for beam NA62 currently taking data for measurement of K + π + ν ν at CERN SPS (400GeV protons) copper TAX after target can run in dump mode by closing TAX, γs not expected! signature for ALPs: 2 coincident γs in LKr calorimeter 1 m achromat Gigatracker Charged anti counter vacuum Large angle photon veto Spectrometer magnet CHOD RICH Liquid Krypton calorimeter Muon veto target tax CEDAR D 81m achromat collimator Large angle photon veto L 135m Straw chambers Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21 spectrometer IRC SAC

22 Extending the Axion-like-Particle reach at NA62? Calorimeter hole for beam NA62 currently taking data for measurement of K + π + ν ν at CERN SPS (400GeV protons) copper TAX after target can run in dump mode by closing TAX, γs not expected! signature for ALPs: 2 coincident γs in LKr calorimeter decay to charged particles? track (studies ongoing) 1 m achromat Gigatracker Charged anti counter vacuum Large angle photon veto Spectrometer magnet CHOD RICH Liquid Krypton calorimeter Muon veto target tax CEDAR D 81m achromat collimator Large angle photon veto L 135m Straw chambers Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21 spectrometer IRC SAC

23 Acceptance for two coincident γs in toy Monte Carlo kinematic acceptance angular distribution: two γ coincident in time in LKr 1.0 y[m ] 0.5 both photons in 0.15m<r<1.13m 0.0 photon distance d 12 >0.10m out x[m] Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

24 Acceptance for two coincident γs in toy Monte Carlo short decay length absorber θ y[m ] Calorimeter hole both photons in 0.15m<r<1.13m l =40 m -1.0 out Photon opening angle too large γ photon distance d 12 >0.10m x[m] Photon opening angle too small long decay length absorber θ kinematic acceptance l = 200 m angular distribution: two γ coincident in time in LKr acceptance: depends on τ, θ, γ red: early decays analytical estimate (mod calo hole) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21 γ

25 Acceptance for two coincident γs in toy Monte Carlo θ θ m a = 200 MeV gaγ = GeV -1 Ea [GeV] m a = 100 MeV gaγ = GeV Ea [GeV] dσf / deadθ [fb / GeV] dσf / deadθ [fb / GeV] kinematic acceptance angular distribution: two γ coincident in time in LKr acceptance: depends on τ, θ, γ red: early decays analytical estimate (mod calo hole) overall acceptance fold acceptance with σ a, explicit dependence on g aγ and m a calorimeter hole little effect as θ peaks at nonzero value good point in evaluating probability of ALP signal Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

26 Combining computation of σ a with the toy MC SLAC 141 g aγ [GeV -1 ] * 1.3 x POT ( 1 day) ** 3.9 x POT ( 1 month) g aγ [GeV -1 ] CHARM SLAC 137 * ** NuCal SN1987a m a [GeV] m a [GeV] red areas NA62 LKr for > 3 events, both photons detected if all backgrounds can be supressed & small losses, even one day of data-taking gives access to uncharted territory this is due to a favourable detector geometry (small D) and the possibility of high-energy protons on a high-z target confront with data (see next slide) and full Monte Carlo as a next step Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

27 From phenomenology towards reality in reality: non-trivial problem (no track!), some ideas but need more thinking and testing 1h appropriate data sample taken in November 2015, TAXes closed, trigger on minimum energy in calorimeter (potentially valuable also for main physics goal: backgrounds) start to make a proper sensitivity estimate based on this data: analysis work plan started... Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

28 Thank you for your attention! Summary: ALPs with > (100) MeV motivated e.g. in DM mediator models suggestion to search making use of existing infrastructure: fast, cheap, complementary physics program novel sensitivity for NA62 in just one day, dedicated dump facility such as SHiP enormous potential not mentioned: collider bounds worked out [Jaeckel et al], (diphoton excess?) results upcoming, stay tuned! I cordially acknowledge excellent collaboration within NA62 and especially with J. Jaeckel, F. Kahlhoefer, A. Ringwald, K. Schmidt-Hoberg, T. Spadaro Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

29 Back-up Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

30 ALPs at even higher masses nearest expert: J. Jaeckel 0 Y inv. LEP LHC CDF Log 10g aγγ [GeV -1] LSW CAST + SUMICO SN1987a HB stars e + e - inv.+γ FCC-ee projection Beam dump LHC data: [Phys. Dark Univ. 2 (2013) ] photon fusion LEP [ ] through ALPstrahlung SN1987a Cosmology Log 10 ma[ev] Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

31 SHiP estimate for coherent production g aγ [GeV -1 ] NuCal ** SLAC 141 * CHARM SLAC 137 SN1987a m a [GeV] proposed dedicated Dump facility for SPS (mainly for Heavy Neutral Leptons) SHiP estimate based on POT (molybdenum, Z = 42) run-time of 5 years, see [ ] D = 70m, L = 50m, calorimeter radius 2.5m note that the ALP sensitivity estimate in SHiP theory paper [ ] is based on incoherent production, i.e. q + q a + γ (cf. next slide) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

32 ALPstrahlung estimate from SHiP theory proposal from SHiP theory paper, figure 5.1 note that orange region from e dumps based on calchep (madgraph similar) q + q a + γ have to deal with composite nature of proton (contrary to coherent production) difficult to compute reliably for ALP masses below 1GeV: for a perturbative calculation to make sense one has to require a large photon p t (proton ), which implies that the ALP can fly out of acceptance additional photon in final state (smaller phase space) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

33 ALP production cross-section m a = 50 MeV log 10 dσ / de a dθ pb GeV θ θ Ea [GeV] Ea [GeV] m a = 500 MeV log 10 dσ / de a dθ pb GeV GeV protons on copper target (normalized to g aγ = 10 4 GeV 1 ) most ALPs produced at around mrad, on optimized detector should be able to cover that region Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

34 Nonzero Photon p t a photon with energy ω = x E beam has a typical transverse momentum of order q t x m p and hence a typical angle of q t /ω = m p /E beam. For a beam energy of 400 GeV the maximum is therefore found around θ 2.5 mrad. produce ALP with m A and E A requires minimum momentum transfer of qmin 2 = m4 A /(4 E A 2 ). If quantity comparable to R1 2 (where R 1 size of the target nucleus), any additional transverse momentum q t > 0 strongly suppressed by the form factor of target nucleus. peak of the differential cross section for non-zero θ disappears for large masses and small energies. Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

35 TAXes and Protons on Target [taken from EDMS , Doble, Gatignon, Girod] POT: flat top: 3 seconds, 2 times in each 42 seconds supercycle: effective factor 0.15 multiplied by protons 1day POT 1 month POT (not including down-times) Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21

36 Heavy Axion-Like-Particles slide stolen from F.Kahlhoefer, MIAPP workshop Axion-like particle as DM mediator pheno: could give large self-interactions in the dark sector DM can annihilate into mediators, which then Decay into SM why is DM evading direct detection? (see left) accessible through rare Meson decays, see e.g could also be evoked for collider phenomenology (diphotons?) [taken from ] Babette Döbrich (CERN) Axion-like particles from proton beam dumps BCTP Bonn, March / 21