Recent results from LHCb

Xuhao YuanOn behalf of the LHCb collaboration

Syracuse University2017-12-16

Outline

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ØLHCb experimentØSelected physics results

q Spectroscopyq CPV: CKM anglesq LFU test with SL & FCNC decaysq Angular distributions in 𝑏 → 𝑠𝑙%𝑙&

ØConclusions

LHCb detector

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Impact parameter: 𝜎() = 20𝜇mProper time: 𝜎0 = 45fs for 𝐵67 → 𝐽/𝜓𝜙 or 𝐷6%𝜋&Momentum: Δ𝑝/𝑝 = 0.4~0.6% (5 − 100GeV/𝑐)Mass: 𝜎J = 8MeV/𝑐M for 𝐵 → 𝐽/𝜓𝑋 (constrained 𝑚P/Q)RICH 𝐾 − 𝜋 separation: 𝜖 𝐾 → 𝐾 ~95%; mis-ID 𝜖 𝜋 → 𝐾 ~5%Muon ID: 𝜖 𝜇 → 𝜇 ~97%; mis-ID 𝜖 𝜋 → 𝜇 ~1 − 3%ECAL: Δ𝐸/𝐸 = 1⊕ 10%/ 𝐸(GeV)�

Int. J. Mod. Phys. A 30 (2015) 1530022

A single-arm forward spectrometer covering 2 < 𝜂 < 5

Reached 7fb&_ØRun1(2010-2012)ØRun2(2015-now)Ø×3 number of 𝐵

(𝜎gghijM~2×𝜎gghij_)

LHCb data taking

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Smoothly runningØOperating with high

efficiency ~ 90%

Observation of Ξll%%

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ØObservation of Ξll% by SELEX [PLB628(2005)18]

ØNo evidence by BaBar, FOCUS, Belle & LHCb

PRL119(2017)112001

ØSearch in LHCb for Ξll%% → Λl%𝐾&𝜋%𝜋%

Ø 𝑁opq = 313 ± 33Ø 𝑚 Ξll%% = 3621 ±0.72 ± 0.31MeV/𝑐M

1.7fb&_

Consistent with LQCD prediction [arXiv:1704.02647]

Part. recon. bkg

Observation of Ωl

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ØThe 𝑐𝑠𝑠 system can be used to test HQET and LatticeØΩl7 → Ξl% → 𝑝𝐾&𝜋% 𝐾& for the search

PRL118(2017)182001

Very narrow

Very narrow

qWhy so narrow? 𝑠𝑠 diquarkq𝐽t valueq𝑐𝑠𝑠 states or pentaquark?

3.3fb&_

CKM angle

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ØTo enable a discovery of NP, we need to know the SM parameters with high precision: CKM parameters

ØNo NP ➯ the unitarity triangle should be the same in all measurements

ØCompare tree level decays and loop level decays is a way to look for inconsistency

Loop onlyTree level

Angle 𝛾 in run 2 data

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ØThe sensitivity to 𝛾 is through 𝐷7 → 𝐾%𝐾& & 𝐷7 → 𝜋%𝜋& decays to CP eigenstates (GLW method)

ØA new measurement using run 2 data exploiting the decay𝐵± → 𝐷∗ → 𝐷𝜋7/𝛾 𝐾±

arXiv:1708.06370

CPV

5fb&_

5fb&_

5fb&_

5fb&_

Combination of 𝛾

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ØAngle 𝛾 can be measured with a large number of different independent methods

ØRecent additions to LHCbcombination

ØSignificantly more precise than previous results from B-factories

ØIs 𝛾 the least well known CKM angle?q𝛼 = (88.8 ± 2.3)° [CKMfitter ICHEP 2016]

LHCb-CONF-2017-004

arXiv:1301.2033

PRD87(2013)052015

𝛾 = (76.8&y.z%y._)°

𝛾 = (68&_{%_y)°

𝛾 = (69&_|%_z)°

BaBar

Belle

sin 2𝛽 and 𝜙6

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ØCPV in interference between mixing and decay

Øsin 2𝛽 &𝜙6 determined via global fit to experiment results

q 𝜙� = 𝜙� − 2𝜙� = −2𝛽� + Δ𝜙� + 𝛿��)

q 𝛽� = arg(������∗

������∗ )

q sin 2𝛽�� = 0.740&7.7My%7.7M7

q 𝜙6�� = −37.6&7.�%7.zmrad

Predictions are very precise

PRD91(2015)073007

sin 2𝛽

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ØDecay-time-dependent CP violation in 𝐵7 → 𝐽/𝜓 𝑒%𝑒& 𝐾67 and 𝐵7 → 𝜓 2𝑆 𝜇%𝜇& 𝐾67

arXiv:1709.03944

3fb&_

3fb&_

Combination of sin 2𝛽

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arXiv:1709.03944ØLHCb Run 1 average value

B factories: 0.679 ± 0.020

Further investigations with Run2 data are needed

SM prediction0.740&7.7My%7.7M7

PRD91(2015)073007

State of 𝜙6

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ØStudied in LHCb, ATLAS and CMS with run1

Ø LHCb new results with 𝐽/𝜓𝐾%𝐾& above 𝜙(1020)included arXiv:1704.08217

ØUncertainty needs to be further reduced

arXiv:1612.07233

𝜙6�� = −21 ± 31mradarXiv:1612.07233

𝜙6�� = −37.6&7.�%7.zmradPRD91(2015)073007

Lepton flavour universality

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ØIn SM difference between interactions of individual charged leptons can only be due to their masses, which leads to precise predictions

ØSensitive to NPq Hiller & Kruger suggest 𝒪(10%) effects from NP

Ø LFU can be tested via 𝐵 decays

Tree level Looplevel

𝑅 𝐷 ∗ =ℬ(𝐵 → 𝐷 ∗ 𝜏𝜈0)ℬ(𝐵 → 𝐷 ∗ 𝜇𝜈�)

𝑅 𝐾 ∗ =ℬ(𝐵 → 𝐾 ∗ 𝜇%𝜇&)ℬ(𝐵 → 𝐾 ∗ 𝑒%𝑒&)

𝑅(𝐽/𝜓),𝑅(Λl∗ ),𝑅(𝐷6

∗ ),𝑅(𝑝�̅�) … 𝑅(𝜙),𝑅(𝐾6),𝑅(𝑝𝐾),𝑅(Λ) …

hep-ph/0310219

𝑅(𝐽/𝜓) in SL 𝐵l%

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ØFirst LFU test using SL 𝐵l% decaysarXiv: 1711.05623

𝑅(𝐽/𝜓) ≡ℬ 𝐵l% → 𝐽/𝜓𝜏%𝜈0ℬ 𝐵l% → 𝐽/𝜓𝜇%𝜈�

SM prediction𝑅 𝐽/𝜓 ∈ [0.25,0.28]

𝑁opq = 1400 ± 300 and 𝑁j¡h¢ = 19140 ± 340

Signal = red histogram

ØFirst evidence of 𝐵l% → 𝐽/𝜓𝜏%𝜈0 (3𝜎)

3fb&_

[PLB452(1999)129, arXiv:hep-ph/0211021, PRD73(2006)054024, PRD74(2006)074008]

𝑅(𝐽/𝜓) results

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ØFor the first time 𝑅(𝐽/𝜓) measured𝑅 𝐽/𝜓 = 0.71 ± 0.17 ± 0.18

Dominated by knowledge of FF and size of simulated sampleq Would be improved in future

Compatible with SM prediction @ 2𝜎 level

arXiv: 1711.05623

𝑅(𝐷∗) using 𝜏 → 3𝜋𝜈

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ØBetter control of 𝜏 vertex with three-prong 𝜏 decay

ØBDT applied for S/B separationØ 3D fit in 𝑞M, 𝜏 decay time & BDT

𝑁opq = 1273 ± 85

3fb&_

𝑞M = 𝑚M(𝑙%𝜈)

𝑅(𝐷∗&) results

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arXiv:1708.08856

The first measurement of 𝑅(𝐷∗) with 𝜏 → 3𝜋𝜈𝑅 𝐷∗ = 0.285 ± 0.019 ± 0.028

𝑅 𝐷∗ ¤¥¦§consistent with SM @ 2.0𝜎

SM

0.304 ± 0.013±0.007 (WA)

2.3𝜎 aboveSM

4𝜎 deviation

Penguin decays

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Ø𝐵% → 𝐾%𝑙𝑙 and 𝐵7 → 𝐾∗7𝑙𝑙ØSM diagrams

ØNext: experimental tests

ØNP may be seen easier in suppressed processes such as penguin decays

𝑅(𝐾) in 𝐵% → 𝐾%𝑙%𝑙&

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ØDouble ratio measured

Ø𝑅 𝐾 = 0.745&7.7z{%7.7¨7 ± 0.036 in 1 < 𝑞M < 6GeVM/𝑐{q 2.6𝜎 from SMq BF for 𝐾%𝑒%𝑒& agree with SM prediction

PRL113(2014)151601

𝑅(𝐾%) ≡ℬ 𝐵% → 𝐾%𝜇%𝜇& /ℬ(𝐵7 → 𝐾∗7𝐽/𝜓(→ 𝜇%𝜇&))ℬ 𝐵% → 𝐾%𝑒%𝑒& /ℬ(𝐵7 → 𝐾∗7𝐽/𝜓(→ 𝑒%𝑒&))

𝐽/𝜓

Not𝐽/𝜓,1 < 𝑞M < 6GeVM/𝑐{

3fb&_3fb&_

𝑅(𝐾∗7) in 𝐵7 → 𝐾∗7𝑙%𝑙&

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ØSM expectationsJHEP 08 (2017) 055

𝑅(𝐾∗7) ≡ℬ 𝐵7 → 𝐾∗7𝜇%𝜇&

ℬ 𝐵7 → 𝐾∗7𝑒%𝑒&q Also measured as a double ratioq No violation of LFU in 𝐽/𝜓 decays

ØSignal yields determined from 𝐵7 mass fits in 𝑞M bins0.045 < 𝑞M < 1.1GeVM/𝑐{& 1.1 < 𝑞M < 6GeVM/𝑐{

3fb&_3fb&_

Result of 𝑅(𝐾∗7)

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JHEP 08 (2017) 055

𝑅 𝐾∗7 = ©0.660&7.7z7%7.__7 ± 0.024(0.045 < 𝑞M < 1.1GeVM/𝑐{)0.685&7.7|¨%7.__ª ± 0.047 1.1 < 𝑞M < 6.0GeVM/𝑐{

Each 𝑅(𝐾∗7) ~ 2.4𝜎 from SM

Scholarpedia 11 (2016) 32643

𝑑ℬ/𝑑𝑞M of 𝑏 → 𝑠𝜇%𝜇&

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ØData generally below model predictions at low 𝑞M

Angular distribution in 𝐾∗𝜇%𝜇&

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ØA cleaner set of observables, where hadronic form factor uncertainties reduced

Results for 𝑃y­

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ØMost angular observables agree with SMØDeviation (2.8 or 3.0𝜎) in 𝑃y­ near 𝑞M = 6GeVM/𝑐{

Scholarpedia 11 (2016) 32643

JHEP 02 (2016) 104

Global fits

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ØTwo separates fitsq LFU observables: 𝑅(𝐾∗), 𝑅(𝐾%) & Belle 𝑒𝜇 differences in angular observables

q 𝑏 → 𝑠𝜇𝜇 global fit: BF and angular in 𝐾∗(𝐾, 𝜙)𝜇%𝜇&, BF of 𝑏 → 𝑋6𝜇%𝜇& from Babar

ØHere Re𝐶¨ _7� is diff wrt SM

prefers Re𝐶¨ _7� ~ − 1 (SM is 0)

SM

SM

PRD96(2017)055008

Conclusion

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Ø LHCb is providing a wealth of excellent resultsqSpectroscopy

üFirst observation of double-charmed baryonüMore strange-charmed baryon observed

qCKM angleüMost precise 𝛾 measured

qThe deviation from SMü LFUüAngular distribution in 𝑏 → 𝑠𝑙𝑙 channels

ØWith the data in Run-2, more exited results expected in the coming year

Thank you