Recent results from the LHCb experiment University of Cincinnati On behalf of the LHCb collaboration
Brief intro to LHCb
The Large Hadron Collider (LHC) proton-proton collisions NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 3/31
LHCb & Dark Matter, astrophysics, astroparticle physics, The LHCb experiment is a general-purpose detector in the forward region of the proton-proton collider LHC @ CERN CMS It can contribute and is contributing to the field of dark matter, astrophysics, etc.! - Certainly not something we had thought about when designing the experiment NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 4/31
Time-dependent CP violation B s D s K The LHCb Detector and Cavern RICH1 MUON CALO RICH2 T MAGNET TT VELO 23 sep 2010 19:49:24 Run 79646 Event 143858637 NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 5/31
LHCb versus ATLAS & CMS pros & cons Detector in the forward region - Detects light states also Smaller instantaneous luminosity Limited acceptance but complementary Excellent vertex resolution - Sees B s oscillations at 40 fs Excellent impact parameter and secondary vertex resolutions Excellent mass resolution - ~0.5% on m(mm) up to 20 GeV Real bonus Unique particle identification performance - Thanks to Cherenkov detectors Allows for a variety of studies Good jet reconstruction - 10-20% energy resolution for jets with pt > 10 GeV - b(c) tagging eff. ~65 (25)% for ~0.3% contamination NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 6/31
How can LHCb contribute to the field of DM physics? Indirect constraints Flavour physics typically more sensitive to higher mass scales than direct searches Constraints on New Physics couplings Direct searches For Majorana neutrinos For Dark Sector signatures Conventional collider searches Constraints on backgrounds in searches E.g. measurement of antiproton production in p-he collisions NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 7/31
Muon pairs in the 2015+2016 data Note : structure given the numerous trigger lines with different requirements NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 8/31
Recent publications relevant to DM & co Measurement of antiproton production in phe collisions at s NN =110 GeV [LHCb-CONF-2017-002] Search for dark photons produced in 13TeV pp collisions [LHCb-PAPER-2017-038, arxiv:1710.02867] Search for long-lived scalar particles in B + K + χ(μ + μ ) decays [Phys. Rev. D 95, 071101 (2017)] Search for hidden-sector bosons in B 0 K μ + μ decays [Phys. Rev. Lett. 115, 161802 (2015)] Search for massive long-lived particles decaying semileptonically in the LHCb detector [Eur. Phys. J. C (2017) 77:224] Updated search for long-lived particles decaying to jet pairs [PAPER-2016-065 arxiv:1705.07332] Search for long-lived particles decaying to jet pairs [Eur. Phys. J. C75 (2015) 152] Search for Higgs-like bosons decaying into long-lived exotic particles [Eur. Phys. J. C (2016) 76: 664] Search for long-lived heavy charged particles using a ring imaging Cherenkov technique at LHCb [Eur. Phys. J. C 75 (2015) 595] Search for Majorana neutrinos in in B 0 π + μ μ decays [Phys. Rev. Lett. 112, 131802 (2014)] Searches for Majorana neutrinos in B decays [Phys. Rev. D 85, 112004 (2012)] I will provide a few highlights NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 9/31
Constraints on backgrounds in astroparticle searches
Antiproton production in p-he collisions [JCAP 1509 (2015) no.09, 023] The ഥp/p ratio is a sensitive probe to DM in the Universe Measured by PAMELA & result confirmed by AMS-02 Current data seems compatible with background from standard sources Biggest uncertainties come from ഥp production! How can LHCb contribute? Measurement of antiproton production in p-he collisions! LHCb can be used as a fixed-target experiment: - Exploit our SMOG device for beam-gas imaging - Injection of noble gases in the vertex detector surrounding the interaction region collision of 6.5 TeV p beam with He - Nucleon-nucleon interactions at s = 110.5 GeV - We acquired 0.4 nb -1 of such data in 2016 (most data from a single 5-hour fill!) NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 11/31
Antiproton production in p-he collisions LHCb-CONF-2017-002 Selection strategy Good primary vertices (PVs) with < 5 backward-going tracks Good quality negative-charge tracks pointing back to the PV (to suppress material interaction and secondaries) Apply particle identification (PID) to bin antiprotons in p and p T NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 12/31
Antiproton production in p-he collisions LHCb-CONF-2017-002 33.7M reconstructed p-he collisions 1.4M antiprotons Double differential cross-section in p and p T : - Spectrum shape in agreement with EPOS simulation [T. Pierog at al, Phys. Rev. C92 (2015), 034906] - But absolute production rate ~1.5 larger! - Excess due for 20% to total absolute cross-section larger - Most of excess due to higher antiproton multiplicity in data NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 13/31
Low-mass particle searches
Search for Hidden Sector bosons Phys. Rev. D 95, 071101 (2017) Study DM sector with portals to SM - Scalar portal (e.g. inflaton) - Axion portal (only in vector K* meson) Look at B K ( ) χ(μ + μ ) decays - b s transition LHCb has largest samples of B K ( ) χ(μ + μ ) decays Careful selection with efficiency independent of m(mm) and t NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 15/31
Search for Hidden Sector bosons Phys. Rev. D 95, 071101 (2017) Model-independent limit - Branching fraction normalised to rare SM decay - Constraints on lifetimes roughly relate to decay lengths ~30mm to 30 cm [Phys. Rev. Lett. 115, 161802 (2015)] Constraints on scalar portal mixing with the SM Higgs inflaton parameter space < 2m t almost ruled out NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 16/31
Search for Hidden Sector bosons Phys. Rev. D 95, 071101 (2017) Supplementary material (tables) can be retrieved from http://lhcbproject.web.cern.ch/lhcbproject/publications/lhcbprojectpublic/lhcb-paper-2016-052.html NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 17/31
Long-lived particle searches
Long-lived particle searches motivation SUSY models with long-lived neutralinos - h 0 χ χ, with χ 3 quarks [Phys.Rev.Lett. 99 (2007) 211801, [hep-ph/0607204]] Hidden Valley models - h 0 π V π V, with π V b ഥb [Phys.Lett. B651 (2007) 374379,[hep-ph/0604261]] Other models predict semi-leptonic decays which LHCb can look for NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 19/31
Long-lived part. decaying semileptonically Eur. Phys. J. C (2017) 77:224 Constrain RPV msugra neutralino decaying to a lepton + 2 quarks signature = muon + jets Experimentally, look for a single displaced vertex with several tracks and a high p T muon Probe long-lived particle mass in range [20,80] GeV and lifetime in range [5,100] ps Limits interpreted in a variety of models, see paper Supplementary material (tables) can be retrieved from http://lhcbproject.web.cern.ch/lhcbproject/publications/lhcbprojectpublic/lhcb-paper-2016-047.html NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 20/31
Long-lived particles decaying to jet pairs LHCb-PAPER-2016-065 Constrain model of Hidden Valley dark pions from SM Higgs decay signature = 2 (b-)jets Experimentally, look for a single displaced vertex with 2 b-jets Update analysis with full run-i dataset Limits for different with π V masses and lifetimes - Example of beam-axis displacement R xy bins proxy for the lifetime NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 21/31
Long-lived particles decaying to jet pairs LHCb-PAPER-2016-065 Observed upper limit versus lifetime on SM Higgs branching fraction for different π V masses and decay modes NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 22/31
Dark Photons
Muon pairs in the 2016 trigger New triggers added in 2016 ability to do both the prompt and the displaced dimuon searches NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 24/31
Search for dark photons LHCb-PAPER-2017-038 Search for Dark Photons (A ) decaying to a muon pair Kinematic mixing with off-shell photon - inherits production mode - can normalise to off-shell photon data-driven analysis Analysis with 2016 data Two types of search: - Prompt-like : 214 < m(a ) < 350 GeV - Long-lived : mm threshold up to 70 GeV First exclusion limits at a non-beam-dump experiment NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 25/31
Search for dark photons LHCb-PAPER-2017-038 Prompt-like mass spectrum M(A) = 0.5 GeV NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 26/31
Search for dark photons LHCb-PAPER-2017-038 First limit on dark photons for m(a ) > 10 GeV NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 27/31
Looking ahead
LHC(b) future NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 29/31
Future sensitivity studies for A m m with run-iii In run-iii LHCb has the amazing goal of running with a software trigger only! huge gains in sensitivity foreseen NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 30/31
In short LHCb is a great general-purpose detector in the forward region - We can do so much more than Flavour Physics LHCb is contributing to the field of DM searches, something that was not anticipated - We provide complementary information to that of the usually named general-purpose detectors ATLAS & CMS So, do not assume upfront that we cannot do some other measurement/study Do get in touch and discuss! 谢谢 Obrigado NCTS Wksp. DM 2017, Shoufeng, Hualien, Taiwan, 13-15 Oct. 2017 31/31