Round Table Discussion at the Final Session of FPCP 2008: The Future of Flavor Physics and CP
aa r X i v : . [ h e p - e x ] S e p Flavor Physics and CP Violation Conference, Taipei, 2008 Round Table Discussion at the Final Session of FPCP 2008:The Future of Flavor Physics and CP
Jeffrey A.Appel
Fermilab, Batavia, IL 60510 USA
Jen-Feng Hsu and Hsiang-nan Li
Institute of Physics, Academia Sinica, Taipei, Taiwan
The final session of FPCP 2008 consisted of a round-table discussion among panelists and audience. The panelistsincluded Jeffrey Appel(moderator), Martin Beneke, George W.S. Hou, David Kirkby, Dmitri Tsybychev, MattWingate, and Taku Yamanaka. What follows is an edited transcript of the session.
1. Question: What are the big questionsin flavor physics at FPCP08?
Jeff AppelMany of us from many places have to write tripreports when we get back. And perhaps when writingthe trip reports we could start with the big questionsin flavor physics that came up here. This is meant tohelp to you write the trip report as well as to focusthe discussions to come. A number of topics weresuggested by people who sent an email. So you canread them here. • CP violation in charged vs neutral B decays? • Mixing induced CP violation in the B s system? • D − ¯ D mixing: How soon can we measure mixingparameter x ? • Spectroscopy: What are the
XY Z states in thecharm sector (counterparts in the bottom sec-tor?)?I don’t need to go through them one by one, but Iwill ask our panel members to begin with what amongthese topics they found most important; what theythink missing from the list. Martin why don’t we be-gin with you?Martin BenekeThe list includes most of the hot topics discussedat this conference. The first two items refer to phe-nomena connected with b → s transitions, where thewindow to new physics is still open widest. However,we have learned in the past few years that the stan-dard flavor theory is working quite well. The muchdiscussed hints in the b → s sector are either not con-clusive (second item) or possess alternative hadronicstandard-model interpretations (first item). The ac-tual observation of D − ¯ D mixing is exciting as aphenomenon, but because of theoretical uncertainties,does not tell us much that we did not know beforeabout new physics.Matt Wingate From the lattice QCD perspective, the most inter-esting thing discussed here was the discrepancy be-tween the HPQCD calculation of f D s and the ex-perimental measurement. The lattice result is quitesound: the non-strange decay constant f D is the onewhich requires more work, namely extrapolating lat-tice data to the physical up/down quark mass. Thefact that f D agrees with experiment while f D s doesnot is an interesting puzzle. The precision quoted forthe lattice result is very impressive, and further de-tails from the authors will allow other lattice expertsto judge the quality of the fits involved. It doesn’tseem plausible to me that the source of the discrep-ancy could be blamed on the fourth-root hypothesisused in staggered-quark calculations.One thing which I am investigating is: What morecan be done on the lattice in studying b → s decays?There are difficulties for the lattice here which are notpresent in b → u decays or neutral B meson mixing.Nevertheless, the b → s decays are of such great inter-est that all approaches, including lattice QCD, shouldbe pushed as far as possible. I think there are calcu-lations we can do which will add to the picture.Dmitri TsybychevI just want to add that whether there is mixing in-duced CP violation in the B s system will remain ahot topic for next couple of years, and hopefully bothD0 and CDF experiments will have updates on theirresults; if not in the summer 2008, then in the fall.There is room for improvement on the precision ofmeasurements of φ s for both experiments. With con-tinuing successful running of the Tevatron, both ex-periments plan to collect up to 8 f b − of data. CDFalready has a sample of 3 f b − . Their current result isbased on a data sample of only 1.3 f b − . The D0 ex-periment has already used the full sample of 2.8 f b − available to date. Therefore it will be able to increaseits sample only when new data are collected. How-ever, D0 plans to improve the selection of B s mesonsdecaying into J/ψφ . As was already mentioned, D0can increase the statistical significance of its sampleby 20% through a better selection. This will directlytranslate to an improvement of the measurement.Additionally, a question still remains involving fpcp08 000
Flavor Physics and CP Violation Conference, Taipei, 2008
SU(3) or U-symmetry. D0 constrains the strongphases involved in the B s angular analysis to thesimilar phases that appear in B d → J/ψK ∗ decays,and are measured at B-factories. The constraint israther weak, and allows for SU(3) symmetry break-ing, which may be as big as 10%. Polarization ampli-tudes, measured in B s and B d decays, are compati-ble within measured uncertainties. This may indicatethat such symmetry exists. The result on phi s doesnot change significantly if the phase constraints are re-moved. However there is no consensus whether sucha constraint should be applied, and one can benefitfrom a stronger theoretical motivation.Jeff AppelYou think that the systematic errors are not comingsoon for how well you can do on this?Dmitri TsybychevThe fit result for the case of free strong phases isprovided in the D0 article in PRL, and agrees verywell within statistical uncertainty with result of theconstrained fit.Jeff AppelAnybody else? Does anybody in the audience wantto add to this list?David KirkbyI think the main question in flavor physics is wherethe new physics is going to show up, if anywhere. Weshould remember also that there are certainly top-ics in flavor physics that have intrinsic interest: spec-troscopy, for example. But how likely is it for newphysics to show up there? To get the audience moreinvolved, how about a show of hands? Where do youthink that the new physics is likely to come from?Raise your hand once at which one of these four youthink is the most promising. So, how about the firstone?Jeff AppelYou have to leave your hands long enough for count.1, 2, 3, 4..David KirkbySo how about the second one, the B s ? Which oneof the four is the new physics most likely to show up?Rahul SinhaThey are connected. If you find ∆ S not equal tozero in B mixing you are likely to find other signals ofnew physics such as a deviation in the small B s mixingphase among other things. They are connected, since∆ S can be written in terms of the small B s − ¯ B s mixingphase.David KirkbyThe second one. What is generated from the B s system? Can we find new physics there? How about D − ¯ D mixing? Well you don’t know, but what’s yourintuition? What’s your gut feeling?Choong Sun KimI thought of the story of the D − ¯ D mixing. Thereis no standard model prediction. How can you findnew physics? David KirkbyHow likely do you think you are going to find some-thing there?Rahul SinhaYes, you can measure the D − ¯ D mixing phase witha precision of about 1degree at Super- B , but we need50 inverse attobarns.David KirkbyHow about spectroscopy? Beyond the standardmodel? QCD is not new physics.Unidentified voiceIt’s kind of obvious that new physics will show upthere, and new particles can contribute to the ampli-tudes like penguin decays or B → τ decays. In myopinion, this will be the best place to look for newphysics.Jose OcarizI agree with the previous comment that it’s a nec-essary condition; but it’s not sufficient. For example,if we think of item 1, I have a feeling that this is moreor less motivated by the measurement of the different CP asymmetry in B → Kπ decay. This is a non-controversial measurement, but the interpretation isnot uncontroversial. There is no way of falsifying thestandard model by this kind of measurement despitethe fact there is potential sensitivity to contributionsfrom non-standard physics.[Comment by Tom Browder added in preparing thisreport: The discussion seemed to imply that there isno possible future resolution of this issue. However,the isospin sum rule proposed by Gronau and Rosneris a model-independent test for new physics. It re-quires much more data ( > a factor of ten) and muchmore precise measurements of A CP ( B → K π ).]Gerald EigenMartin, you brought up the b → s transitions. Iagree with you that these are important. Since point1 is rather general, wouldn’t you rather split theminto subtopics that are associated with different pointsthan including them all under point 1?Martin BenekeI was thinking of mixing-induced CP violation.Would you like to include b → sℓℓ ?Gerald EigenYes, and also the b transitions involving s ¯ s , like φK s , η ′ K s , etc. The leptonic penguins clearly belongunder point 1, while the gluonic penguins fit betterunder point 2.(George) Wei-Shu HouI know I am viewed as a fanatic, saying that fourthgeneration this and that., fourth generation for every-thing. I actually quite agree with what Martin andJose said, and that this kind of discussion can be end-less, and we are not going to go very far. But theconverse is not true; that if you show that in somenew physics model you can generate an observed ef-fect, it would still be of interest. So [going into a shortpresentation] this result here is published in 2005, and fpcp08 000 lavor Physics and CP Violation Conference, Taipei, 2008
3I give you the diagram. I have said many times dur-ing the conference, that having a t’ would bring inlarge Yukawa couplings and new CP violating CKMelements. Our study was re-done at next to leadingorder in PQCD, and the effect on DCPV differencewas not diluted. And there is another thing, that itdoes push down ∆ S .It’s not sufficient to generate the central value ofthe experiment, but to me that is very interesting.The two things mentioned in this conference are ofnote to me. One thing.Maybe I pull this slide [fromDerek Strom’s talk] back. If you look at this, hereis the Standard Model expectation for φ s , and hereare all four different, related measurements. All themeasured values fall to the left. And here is the ac-tual published prediction from 4th generation (whichis smack in the middle of the experiments). I alreadystated something like this, large sin(2Φ B s ), in 2005.This is on the record. At the moment, I am not aUT-fitter fan, and nobody here is. I am not on theIAC. I would have voted for them to be here, just forthe debate. At the moment, you know, experimen-tally one can not yet say too much. It’s not incon-sistent with the Standard Model. I do point out thatthese numbers normally would be scattered (if the SMis correct), but they are not. The error bars will getreduced, say in next two years, from 1.35 inverse fem-tobarns of data, to 3 to 5 to 8. In the last year ortwo, I used to say that if the central value stays, Iwould then be willing to bet a good bottle of red winethat the 4th generation is real. Starting a year agoat FPCP in Slovenia, the data seem to be heading inthis direction. Now here [another slide on A F B fromEigen’s talk] is one thing that Gerald brought up butdidn’t really go through. The green line in the Belleplot is marked ”C9, C10 sign-flipped”, which is equiv-alent to C7 sign flip. The blue line in the BaBar plotis for the Standard Model, almost zero, but slightlynegative. Now the upper figure was actually shownby Dmitri [Tsybychev] in his talk. The blue dashedcurve, is the fourth generation differential A F B , andthe marked red line gives roughly the lower q binhere. So you can understand why the Standard Modelis slightly negative and close to zero; because belowthe zero is negative. Sorry that the sign conventionis opposite to the B-factory experiment. And abovethe zero is positive but there is a bit more negativethan positive so that you get the blue zero, or close tozero, of the SM in the BaBar plot. But in our fourthgeneration analysis the line moves down. So the zeromoves further down, and there is not much negativepart but large positive part; so it’s more consistentwith Belle/BaBar results. And I think it was Uli whoraised this issue, you know, complaining what is stillcalled by experimentalists the C7 sign flip. This isbasically a way that experimentalists say that thereis a deviation. And this is why I stressed that I wantto treat these things more generally, to allow com- plex Wilson coefficients. This gives the shaded area.I don’t want to go into any further details. Let mechange tone and say — I am willing to bet a goodbottle of Champagne now, if you want to take up theorder. Why? Now this [yet another slide] is the stan-dard folklore that Standard Model CP violation is10 − . Here is the Jarlskog invariant, and A here, theinvariant CPV area, is like 10 −
5. But the real suppres-sion is coming from these small masses. So if you putin numbers, when you normalize properly with, say,the electroweak phase transition temperature, you getthis 10 − . Now you see the fourth generation doesmiraculous stuff here because it naturally has largeYukawa couplings. So if you shift by one generation,this m c − µ becomes m t − m c , etc. This gives rise to avery large enhancement. Well, it is still a suppressionfactor, but the m b − m s alone is the only suppression.So this gives a 10 gain, where about a factor of 30is from the b → s CP violating analysis. OK, butthe factor of 30 compared to 10 is nothing, so longthat this factor of 30 is not 10 , or something. So wehave a very large enhancement factor compared to theStandard Model three generation Jarlskog invariant.I think this is another proof that Nature is more inge-nious than anyone of us here. But for me, to be ableto jump back to put the CP violation within Yukawasector to be relevant for baryogenesis, that’s why I sayI am willing to bet a good bottle of Champagne now,... but only for ten people, OK?Choong Sun KimI do not know all the details of fourth generation,but I have some simple questions. First, as you know,and as everyone knows, this fourth generation neu-trino mass is quite heavy, >
45 GeV. So why do wehave such a heavy neutrino, much different from thefirst three generations? That’s very strange to me.This kind of thing comes out more naturally if we havesomething like a string-inspired E(6) model, whichpredicts rather heavy vector-like quarks, unlike thefourth generation.(George) Wei-Shu HouWell, there is a very simple answer to that. Vec-tor like quarks will not have this enhancement. Theseare not masses, these are Yukawa couplings. Diracmasses go into the denominators, propagators and de-coupling. So we can not have enhancement.Choong Sun KimSomething like Kaluza-Klein or some other excitedstates. I think probably a similar result will come outgenerally without a so-heavy neutrino problem.(George) Wei-Shu HouYea, OK. I can not argue with Kaluza-Klein. Theyare all legitimate, but this one (4th generation) iswithin Standard Model dynamics! Now for neutri-nos, we firmly know there are only three light ones.But since 1998, as compared to 1989, we also learnedthat neutrinos have mass. So it’s a much richer sectorthan we knew of. Furthermore, you didn’t mention fpcp08 000
Flavor Physics and CP Violation Conference, Taipei, 2008 electroweak precision tests, right? There is a recentpaper by Kribs et al (Plehn, Spannowsky and Tait),which refutes the very stringent application of preci-sion test against the fourth generation in the PDG.list. So it’s not ruled out. But whatever you say, Iam just saying this more than ten-order-of-magnitudegain is so enormous. I use this to argue that, despiteelectroweak precision tests, even the neutrino stuff,the 4th generation is fairly legitimate. The thing is,when you have high scale CP violation for baryoge-nesis, such as leptogenesis, you tend not to have alaboratory test. It’s a matter of physics in the usualsense.Taku YamanakaI didn’t vote for any of the four items up there.Since I am an experimentalist, and since I work onkaons, I will vote for kaon physics experiments. Thesensitivity of a K L → π ν ¯ ν experiment will first godown by three orders-of-magnitude, from O(1E-8) toO(1E-11). Even beyond the Grossman-Nir limit, thereis a two-orders-of-magnitude parameter space for newphysics to appear. So, do you want to vote for a 10percent effect, or do you want to vote for a large pa-rameter space with two orders-of-magnitude? I wouldvote for a two-orders-of-magnitude effect.
2. Question: What are the bigflavor-physics questions to come?
Jeff AppelThere is another way to continue this discussionwhich is the second question. That is, what are likelyto be the big flavor-physics questions after the firstTevatron or LHC signal beyond the standard model?And a corollary question is what would be the flavor-physics questions if we don’t see a new signal at LHC?The answer given for the first part is that the in-teresting flavor-physics question will depend on whatyou see. However, almost anything you see will havemultiple possible answers, multiple models which canexplain it. This may mean that there are sensitivitiesto flavor physics across the board. In fact, I don’tthink a signal in a particular channel will lead to onlyone flavor-physics parameter that you want to look at.That’s how I guess I would put it.Tom BrowderIf a signal really shows up early at the LHC, I thinkthe big question will be how any new particles at LHCdo not produce flavor changing neutral currents. Thetheorists will have to find brilliant ways for cancella-tions to not produce flavor changing neutral currents,not just produce a new model.Jeff AppelSo you don’t think there will be big signals fromLHC? I didn’t mean to put too many words into yourmouth. Anybody on the panel want to respond to thismore ambiguous question? David KirkbyI think it is easy to imagine new physics at LHCwhere you wouldn’t really know what to do at theSuper-B-factory. So maybe the challenge to the au-dience is ”Can you think of something we may findat the LHC where it would be unclear what to do inflavor physics?” Are there other scenarios? Let’s talkabout that.Rahul SinhaIf you see a signal of something at the LHC, youwant to make sure that the theoretical parameterscorresponding to your favorite model/scenario, andthat are consistent with the signal, are not actuallyruled out by precision tests; and B physics wouldprovide a precision constraint, through loop contri-butions. Therefore, you want to make sure that B data is consistent with the scenario and the observedsignal. That is one way again of using flavor physics.David KirkbyThere are strong constraints from the data we al-ready have.Rahul SinhaThis is not enough. As to whether the current fla-vor constraints are good enough - let me say we needto improve; we need as much improvement as pos-sible. With the LHC alone, we may see a signal ofnew physics, but we may not be able to figure outwhat kink of new physics it corresponds to. Here iswhere flavor physics comes in, ruling out or findingconsistency among different models given a particularsignal. The better the precision, the better the con-straints. One requires flavor physics to enable pinningdown what is the new physics.Martin BenekeWe discuss flavor physics in the context of theTeV scale. In doing that, we almost always implic-itly assume that electroweak symmetry breaking iscaused by some weak-coupling phenomena. That’snot guaranteed. An entirely different way of seeingthings would be needed if it turns out that electroweaksymmetry breaking happens through some QCD-likestrong-coupling mechanism. Then the flavor-physicspuzzle is more severe, because if there is no weak cou-pling at the TeV scale, we would know that flavorphysics is probing much higher scales which are dis-connected from TeV scale. So, indirectly, one of thebig flavor-physics questions to come and be answeredis what causes electroweak symmetry breaking.Keh-Fei LiuI wonder if one of you could comment on neutronelectric dipole moment in terms of its discovery poten-tial, and if there can be some effect found in the nextcouple of years. Will the new physics be orthogonalor complimentary to this flavor physics?Jeff AppelThe coupling to the neutron electric dipole momentfor any of these questions. George?(George) Wei-Shu Hou fpcp08 000 lavor Physics and CP Violation Conference, Taipei, 2008 E T signal atthe LHC. I would like to get an opinion as to whetherflavor physics can help in pinning down the nature ofthe new physics. With flavor-physics constraints in-cluded, it would be interesting to come up with signalsthat can help to say whether it is SUSY or not SUSY.Dmitri TsybychevIf you have missing E T , it could be anything. Itcould be supersymmetry. It could be a leptoquark.It could be extra dimensions. There are a number ofscenarios that will result in large missing E T .Rahul SinhaSure. But, what is it that should be really watchedout for, say, for SUSY or other new physics, and whatkind of measurements in flavor physics can actuallyhelp distinguish between the kinds of scenarios. Is itpossible to do that? Anybody?Jeff AppelI think the point is that too many things havemissing-energy signals to say that this or that is thespecific answer.Tom BrowderThere is a sort of a worldwide effort, at CERNand other places. People are writing very thick yel-low books about the connection between flavor physicsand the physics at LHC. They do consider lots of dif-ferent scenarios in the possible impact of all the ob-servables in B physics. You may find reading these ar-ticles boring now because we don’t have a new physicssignal at the LHC to look at. But there have beenpretty substantial efforts and a lot of papers on this.Enrico LunghiI have a general comment on the first two ques-tions. ATLAS and CMS are mostly ”flavor-diagonal”experiments. On the one hand, they will tell us themass scales and the tree-level structure of whatevernew physics model is realized in nature. On the otherhand, the quantum structure of the theory (e.g. loopeffects) will be hardly accessible. The latter task isperfectly suited for flavor-physics experiments, thatwill act as a tie-breaker among the several equivalent new physics models that will emerge from the firstanalyses of LHC data. Of course, these kinds of stud-ies require inputs from ATLAS and CMS. Once a fewmasses and processes are known, one can constructcomplete models and predict which flavor observablesare expected to deviate from the SM predictions. It isalso possible that ATLAS and CMS will not find anynew physics. In this case, flavor physics (including lep-ton flavor violation) will allow us to access to muchhigher scales (e.g. hundreds of TeV). There are twoscenarios. If ATLAS and CMS find TeV-scale newphysics, flavor physics will help to find out the de-tailed structure of the theory. If, on the other hand,new physics turns out to be beyond the reach of di-rect production at the LHC, we can still explore it viasuper-rare processes (e.g. lepton flavor violation).Choong Sun KimI have some unrelated questions for Hsiang-nanand Martin about the previous discussions. Every-one knows that we, within the standard model, cannot calculate the B to π π branching fractions. Isthat new physics?Martin BenekeNo.Choong Sun KimBecause the error is quite small. The experimenterror is small.Martin BenekeBut the theoretical error is not so small.Choong Sun KimBut you can explain all others except for π π .Even B to ρ ρ , which has exactly same quark di-agrams as π π , can be predicted rather well. Whenthe measurements began, it was quite different - the-ory predicted only 1/3 of the experimentally measuredbranching fraction. So I think today’s value is kind ofa post-diction. You just changed the input param-eters. Therefore, even though we think it is rathertrivial, like the color-suppressed tree, it can be some-thing else - like beyond the standard model.Martin BenekeWe have learned that the dynamics behind thecolor-suppressed tree amplitude is very different fromthe naive factorization picture, and also understandwhy the theoretical uncertainties are large for this am-plitude.Rahul SinhaI just want to ask something since you raised thequestion about factorization and naive factorization.Naive factorization works so well in D decays. Weall remember the classic paper of Bauer, Stech andWirbel. Factorization, however, does not work so wellin B decays as is evident from data. Is there a goodexplanation for that? Why does factorization workbetter for D decays and not that well for B decays?Martin BenekeI wouldn’t say that this is true. In B decays, wediscuss many more challenging observables than just fpcp08 000 Flavor Physics and CP Violation Conference, Taipei, 2008 branching fractions of tree-dominated decays; suchas penguin-dominated decays, CP asymmetries, andstrong phases.Rahul SinhaLet us just go back to branching ratios for modeslike Kπ , ππ and ... These things work so well in D decays, but not that well in B decays.Hsiang-nan LiBut I think this question does not belong to this cat-egory. I think it’s still too early to have any concreteconclusion because currently the theoretical precisionis just up to next-to-leading order, right? So there isnext-to-next-to-leading order, next-to-next-to-next toleading order. There is a long way to go.
3. Question: What are the connectionsbetween observations in the quark andlepton sectors?
Jeff AppelThis is pretty technical for the round-table level ofdiscussion. I guess I’d like to move on to our nextquestion. I don’t have a lot of questions. Don’t gettoo scared. I wonder about the connection betweenthe flavor observations in the quark and lepton sectors.Do we understand these? Or, do we have to wait toget to Plank scale to figure it out.Choong Sun KimThe sin( θ ) in neutrino-sector mixing and sin( θ )in the quark sector, now adding up those 2 mixingangles comes up to about 45 degrees. It could be anaccident. Or maybe there is some kind of connec-tion between the quark sector and the lepton sector.People say it’s complementarity, something like that.Quark-lepton complementarity. Maybe there is somereason behind it, or is it an accident?
4. Question: Is there a flavor-physicscommunity, and if so, has it articulatedits case well enough?
Jeff AppelOne reason why I put this question in here is to ad-dress the nature of this conference and our community.I use the singular form, our community, the flavor-physics community which covers quarks and leptons.This is the physics we have discussed at FPCP 2008.Have quarks and leptons been brought together at thismeeting more strongly than in the past because of CP violation only, or there is something more fun-damental that makes them part of the same commu-nity? And if so, has this community articulated thecase for support of both axes strongly enough? I amthinking of the priorities that have been expressed inthe United Kingdom and in the United States. We also have heard about the delay in kaon physics atJ-PARC, and so on.Taku YamanakaWell, let me first speak about the situation inJapan. The High Energy Physics Committee inJapan, of which I am also a member, wrote up a reporton what to do in the future. In that report, we statedtwo things. One is, approach the high energy frontier,including LHC and ILC etc. We also stated that theintensity frontier, especially flavor physics, is impor-tant. This is especially true because in Japan we haveBelle and the neutrino program. The experiments arevery popular and are being supported. J-PARC is thekey facility for neutrino and kaon experiments. Eventhe people pushing for the ILC are supporting the J-PARC program, because if J-PARC fails, then there isno linear collider. From the viewpoint of the fundingagency, that’s very clear.If the question is, is there a flavor-physics commu-nity in Japan, the answer is yes. The people work-ing on kaons, B physics, and neutrino physics, experi-mentalists and theorists, have joined forces and won a”Grant-in-Aid for Scientific Research on Priority Ar-eas”, titled ”New Developments of Flavor Physics”.The project is supported for 6 years, and the fundis being used for building the T2K and Opera exper-iments, the J-PARC kaon experiment, B physics atCDF, and Belle. We get together every year to have asmall workshop to present all the new findings. Thisis really making a close community of people rangingfrom young students to older professors working onvarious experiments and theories, all on flavor physics.Martin BenekeIt may be unpopular to say this, but talking to peo-ple outside and even within the flavour physics com-munity, one may get an impression that flavor physi-cists had their chance to find new physics. They didnot, so it is time to move on to the next thing - LHCphysics. If something shows up there, then we can goback to flavor physics to try to sort things out. Wemay be blamed ourselves for that because we havebeen talking too much about new physics and obscure2 σ effects, and didn’t succeed to create interest in theintrinsic physics itself, in the phenomena.I am fascinated and mystified how neutrino physicsis succeeding in this respect – measuring a mass ma-trix in the lepton sector, which is after all not so dif-ferent from measuring the CKM matrix. And there iseven less prospect of discovering new physics by de-termining θ than there is in V ub !Jeff AppelThere is an interesting corollary to the way you putit. In terms of selling the physics these days, onetries to sell physics as ”paradigm-changing” discover-ies. What is the argument you would make to sellour physics, whatever it is? The first thing one looksfor is what people call paradigm-changing discoveries,right? How would you sell the physics that you are fpcp08 000 lavor Physics and CP Violation Conference, Taipei, 2008 B factory. I don’t believe that it’snuclear physics.Jeff AppelAnd it’s interesting because it was a surprise? Orinteresting for another reason?Bruce YabsleyAgain, it’s interesting because it’s a surprise. Now,if we get into a position where we discover somethingthat is both surprising and interesting! Maybe wehave to spend a few years in training on how to talkto guys from the newspapers. Maybe we just do.David KirkbyMaybe one way to answer your question is to lookat the nuclear physics community because they are, atleast in the US, well funded; and what they are doingis not so different from spectroscopy in heavy quarks.Rahul SinhaThe fact is that we initially set up the B factoriesto test the CKM hypothesis. We have succeeded; wehave done that. We have not only succeeded in doingthat, but we have learned a lot more. We have newresonances and many puzzles about them. This is atthe very least ”surprising”. So in that sense, thereis no way to say that we have not actually had verygood physics output. Somehow, B physics efforts havebecome the victim of various constraints dictating thedirections in physics, e.g. our desire to find a wayprobe the Plank scale as fast as possible. Eli RosenbergLet me say something that has already been said.The first slide you put up there. It all had to do withwhere new physics is going to be found. You alreadybrought in the concept that to sell anything, it hasto be something new. And on your second slide, thereaction to what happens in the Tevatron and LHC.God help this field if nothing is found in those places.This conversation becomes entirely irrelevant simplybecause we have oversold the idea that we have to findsomething new. Now I have a feeling that if we wentback to 30, 40 or 50 years ago, when particle physicswas a virgin, people were working on precision mea-surements of electromagnetic interactions. We musthave felt exactly the same way you are feeling in thisroom now - that somehow we were undervalued bylooking at things where you could make precise mea-surements. And the real argument is, we are workingin the area where you can make precise measurements,where you can look for new things like lepton flavorviolation. We’d like to measure D mixing because wedidn’t expect to see much of it. It’s interesting, andit has intrinsic interest of its own, period. Whetherit’s going to be something new or not, that is a dif-ferent issue. Now, how you sell that to our fundingagencies is where the problem seems to come in. Thesame thing happens in the K meson sector. The K meson sector had a resurgence at one point after be-ing pushed down for a long time. So this has been acontinuing problem. But I think part of the problemis that we have gotten so big and so expensive that weoversell everything. The field as a whole has oversoldeverything. This is what you have to do. That’s whyyou read the headline about 600 physicists failing tofind this or that; because we said we were going to findit. You know, we sold the SSC as if we could do ev-erything except cure baldness. So I think we just havea PR-reality problem about what science is about.(George) Wei-Shu HouI would like to make several remarks touching on allthat has been said. I think that on neutrino physics,I held back on one question that I used to ask. IfI take V ub , it’s very hard to extract, correct? Butif we take the V ub analogy, because neutrino peoplehave had ten spectacular years, this is in part becauseof the very large mixing angles. They could not or-dain that, right? So if I take V ub or even V cb , our θ or θ for neutrinos, I don’t see a program yetto measure something of that strength for θ . Theyare entering a hard time. Without that (a large θ ),forget about CP violation in the lepton sector. OK,Majorana neutrinos, (neutrinoless) double beta decay,there is always some discovery potential. But they arenot really doing better than we are. I don’t know how,in the last ten minutes, we entered such a very gloomymood. I think we actually have a good situation. TheLHC is starting. The Tevatron is still working veryhard. We are seeing things here and there. We are, fpcp08 000 Flavor Physics and CP Violation Conference, Taipei, 2008 of course, used to seeing things disappear from beforeour eyes. But that’s how it is; right? Seeing somethingemerge and then disappear; hoping that one of them istrue. And I think this mixing-dependent CP violationphase (in B s ) is of course the way to go. But, maybewe are overselling it. It may be a PR problem, butwe do have genuine indications, not just challenges.So I like what Enrico said, I think at LHC, ATLASand CMS analyses will find the scale. The New Parti-cles will likely be extrinsic to flavor. However there isalso LHCb, right? I guess we go back to Question 2.What if we see nothing beyond the Standard Model?Maybe we see the Higgs, maybe we don’t. But if wesee nothing, and LHCb will measure sin(2 φ s ) to plusor minus 4 percent, no charged Higgs, no SUSY. Thenno matter what PR we do, you can not get the nextbig machine.But I am optimistic about both LHC proper, thehigh energy frontier, and LHCb also. I am also afull supporter of the Super KEKB or Super B -factory.Because it’s really a PR question again. A Super B -factory is a multi-purpose facility. And speaking fromAsia, I am even more supportive of this. Asia is rising.It has the population, etc. I would fully support iteven just only on that account. That it is a projectto work on, to go forward. And if not a discovery atthis stage, then there will be a discovery at the nextstage. To me, Super KEKB is a regional cooperationconcern.Jeff AppelIn order to move to a more positive direction, per-haps there are other questions people would like toaddress to the panel, or to each other before I get tomy last question?Bruce YabsleyJust inspired by the previous discussion, I wouldnote that when the LHC turns on, the field is goingto undergo a kind of basic change. The kind of infor-mation we are using to decide what studies to do, andhow to do it, is going to change. Now, the momentsomeone puts a preprint on hep-ph, everyone at the B -factories, drops everything they are doing to pursuethe suggested analysis, or something like this. What’sgoing to happen now is that we are going to get somesign of a particular mass scale. And that’s going tohave an influence on the things we should be studying.But the influence is going to be a hundred percent, be-cause it’s going to determine what the new physics is,presumably, and more than one model will be possi-ble. Here my question is: do we have a mechanism sothat we have a while to think about how we are goingto be influenced by the new information. Or, are wegoing to be driven by some prejudice that what we see,is what we know, and so suddenly everyone rushes inparticular directions like ten-year-olds playing soccer.The situation really is going to change. I am wonder-ing if we thought forward to what happens when wesee data. Jeff AppelI think there is plenty of evidence that the com-munity is a very good at rushing together in singulardirections, in effect, ten-year-olds playing soccer asyou called it. We also did this when the J/ψ wasdiscovered. Every experiment asked if they could seeevidence of that signal.Enrico LunghiI would like to make a comment on the impossibilityof a null result at the LHC. In fact, unitarity tells usthat either we’ll find at least one Higgs particle. Oth-erwise, some other phenomena have to happen (e.g.strongly-interacting vector bosons, new strong reso-nances, ...). In any case, even if just a SM-like Higgsis found, we still need a linear collider to study itsproperties. I don’t think that we can really go thereand see nothing.Eli RosenbergBecause you are so convinced, and we have beentold that we will. And if we see nothing, it is themost fascinating physics result of all - except that itwill kill the field. Aside from that, ... I rest my case.Then why do we have to build it? Because we aregoing to see something.Choong Sun KimI have one question not related to politics or any-thing like that. We know that George proposes afourth generation. But if there is a fourth generation,it is supposed to violate unitarity in three generationsbecause, effectively, the 3 by 3 part of the larger 4by 4 matrix is non-unitary. OK. What I want to askis another thing, about gamma in the unitary trian-gle. The gamma or alpha measurement is not actuallymeasuring gamma or alpha. It’s beta plus gamma, forexample. So my question is, is it possible that LHCb,or Super-B, or any future B-factory can find the 3by 3 CKM matrix non-unitary? Is it possible to findnon-unitarity or not?Jeff AppelYes, anybody working in B factories would say yes,you can find the triangle does not close. It is notunitary and there is going to be something else, somenew physics.Chung-Sun KimThe measurement of gamma or alpha is from the π − ( α + β ). So by definition, you are just taking theangles as from a triangle.Jeff AppelThe sides have to work too, right?Eli RosenbergGamma, perhaps from a Dalitz analysis, maybefrom the Υ(5 S ). Does that beta plus gamma matchthe beta plus gamma you get when they interfere?That’s the test. And that’s equivalent to test unitar-ity; whether the standard model is working. That’swhat is, in short hand, called alpha. I agree with you.Nobody measures alpha, but measures π − ( β + γ ).Rahul Sinha fpcp08 000 lavor Physics and CP Violation Conference, Taipei, 2008 γ , or one of the anglesmeasured, has to be from outside of the B d , to see abreakdown of unitarity. It is well known that if youmeasure the three phases using just B d , the effect ofnew physics will cancel out. In addition, the otherthing one can do is to measure both sides and theangle and then check if the triangle closes.Jeff AppelThe same triangle.Choong Sun KimThe measurement of γ or α is from π − ( α + β ) or π − ( β + γ ). So, by definition, you are just forcing atriangle if you do not measure the 3 angles indepen-dently. Also, beta from B → J/ψK s can effectivelyinclude new physics, too.Rahul SinhaYes. But, you can also measure gamma, outsidethe B d system. There is a method to measure it using B s → DK . If you do that, then there is no problem.You can detect the breakdown of unitarity withoutmeasuring the side.Jose OcarizAnother way of saying it is that you are measur- ing 4 parameters with 10 observables. If you have noconsistency, you have no unitarity.
5. A final question.